Identifying Minerals | Earth Science

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These include color, crystal form, hardness, density, luster, and cleavage."> <meta name="keywords" content="science, education, STEM, math, biology, chemistry, physics, earth science, online learning"> <meta name="viewport" content="width=device-width, initial-scale=1.0, shrink-to-fit=no"> <meta name="msvalidate.01" content="D8E20F39AD48052260032E56DE409970"> <script type="application/ld+json"> { "@context": "http://schema.org/", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://visionlearning.com/en/library/earth-science/6/identifying-minerals/130" }, "name": "Identifying Minerals", "headline": "Identifying Minerals: Characterizing minerals' physical properties", "author": { "@type": "Person", "name": "Anne E. Egger, Ph.D." }, "datePublished": "2005-05-15 19:33:15", "dateModified": "2017-02-12T08:30:00+05:00", "image": { "@type": "ImageObject", "url": "/img/library/moduleImages/featured_image_130-23061209065745.jpeg", "width": 696, "height": 464 }, "publisher": { "@type": "Organization", "name": "Visionlearning, Inc.", "logo": { "@type": "ImageObject", "url": "http://visionlearning.com/images/logo.png", "width": 278, "height": 60 } }, "description": "Minerals are classified on the basis of their chemical composition, which is expressed in their physical properties. This module, the second in a series on minerals, describes the physical properties that are commonly used to identify minerals. These include color, crystal form, hardness, density, luster, and cleavage.", "keywords": "science, education, STEM, math, biology, chemistry, physics, earth science, online learning", "inLanguage": { "@type": "Language", "name": "English", "alternateName": "en" }, "copyrightHolder": { "@type": "Organization", "name": "Visionlearning, Inc." }, "copyrightYear": "2005"} </script> <meta property="og:url" content="https://visionlearning.com/en/library/earth-science/6/identifying-minerals/130"> <meta property="og:title" content="Identifying Minerals | Earth Science | Visionlearning" /> <meta property="og:type" content="website"> <meta property="og:site_name" content="Visionlearning"> <meta property="og:description" content="Minerals are classified on the basis of their chemical composition, which is expressed in their physical properties. This module, the second in a series on minerals, describes the physical properties that are commonly used to identify minerals. 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<li><a href="/en/library/environmental-science/61/ecosystem-services/279">Ecosystem Services</a></li> <li><a href="/en/library/environmental-science/61/population-biology/287">Population Biology</a></li> </ul> </div> <button class="accordion__button" id="acc-button-earth-cycles" data-accordion="button" aria-controls="acc-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/environmental-science/61/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/environmental-science/61/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-research" 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</button> <div class="accordion__panel" id="acc-panel-general-science" data-accordion="panel" aria-labelledby="acc-button-general-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-methods" data-accordion="button" aria-controls="acc-panel-methods" aria-expanded="false"> <span class="accordion__button__label"> Methods </span> </button> <div class="accordion__panel" id="acc-panel-methods" data-accordion="panel" aria-labelledby="acc-button-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-scientific-method/45">The Scientific Method</a></li> </ul> </div> <button class="accordion__button" id="acc-button-measurement" data-accordion="button" aria-controls="acc-panel-measurement" aria-expanded="false"> <span class="accordion__button__label"> Measurement </span> </button> <div class="accordion__panel" id="acc-panel-measurement" data-accordion="panel" aria-labelledby="acc-button-measurement" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/the-metric-system/47">The Metric System</a></li> </ul> </div> <button class="accordion__button" id="acc-button-physical-properties" data-accordion="button" aria-controls="acc-panel-physical-properties" aria-expanded="false"> <span class="accordion__button__label"> Physical Properties </span> </button> <div class="accordion__panel" id="acc-panel-physical-properties" data-accordion="panel" aria-labelledby="acc-button-physical-properties" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/general-science/3/temperature/48">Temperature</a></li> <li><a href="/en/library/general-science/3/density-and-buoyancy/37">Density and Buoyancy</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-math-in-science" data-accordion="button" aria-controls="acc-panel-math-in-science" aria-expanded="false"> <span class="accordion__button__label"> Math in Science </span> </button> <div class="accordion__panel" id="acc-panel-math-in-science" data-accordion="panel" aria-labelledby="acc-button-math-in-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-equations" data-accordion="button" aria-controls="acc-panel-equations" aria-expanded="false"> <span class="accordion__button__label"> Equations </span> </button> <div class="accordion__panel" id="acc-panel-equations" data-accordion="panel" aria-labelledby="acc-button-equations" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/unit-conversion/144">Unit Conversion</a></li> <li><a href="/en/library/math-in-science/62/linear-equations/194">Linear Equations</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-i/206">Exponential Equations I</a></li> <li><a href="/en/library/math-in-science/62/exponential-equations-ii/210">Exponential Equations II</a></li> <li><a href="/en/library/math-in-science/62/scientific-notation/250">Scientific Notation</a></li> <li><a href="/en/library/math-in-science/62/measurement/257">Measurement</a></li> </ul> </div> <button class="accordion__button" id="acc-button-statistics" data-accordion="button" aria-controls="acc-panel-statistics" aria-expanded="false"> <span class="accordion__button__label"> Statistics </span> </button> <div class="accordion__panel" id="acc-panel-statistics" data-accordion="panel" aria-labelledby="acc-button-statistics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/introduction-to-descriptive-statistics/218">Introduction to Descriptive Statistics</a></li> <li><a href="/en/library/math-in-science/62/introduction-to-inferential-statistics/224">Introduction to Inferential Statistics</a></li> <li><a href="/en/library/math-in-science/62/statistical-techniques/239">Statistical Techniques</a></li> </ul> </div> <button class="accordion__button" id="acc-button-trigonometric-functions" data-accordion="button" aria-controls="acc-panel-trigonometric-functions" aria-expanded="false"> <span class="accordion__button__label"> Trigonometric Functions </span> </button> <div class="accordion__panel" id="acc-panel-trigonometric-functions" data-accordion="panel" aria-labelledby="acc-button-trigonometric-functions" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/math-in-science/62/wave-mathematics/131">Wave Mathematics</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-physics" data-accordion="button" aria-controls="acc-panel-physics" aria-expanded="false"> <span class="accordion__button__label"> Physics </span> </button> <div class="accordion__panel" id="acc-panel-physics" data-accordion="panel" aria-labelledby="acc-button-physics" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-light-and-optics" data-accordion="button" aria-controls="acc-panel-light-and-optics" aria-expanded="false"> <span class="accordion__button__label"> Light and Optics </span> </button> <div class="accordion__panel" id="acc-panel-light-and-optics" data-accordion="panel" aria-labelledby="acc-button-light-and-optics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/the-nature-of-light/132">The Nature of Light</a></li> <li><a href="/en/library/physics/24/electromagnetism-and-light/138">Electromagnetism and Light</a></li> </ul> </div> <button class="accordion__button" id="acc-button-mechanics" data-accordion="button" aria-controls="acc-panel-mechanics" aria-expanded="false"> <span class="accordion__button__label"> Mechanics </span> </button> <div class="accordion__panel" id="acc-panel-mechanics" data-accordion="panel" aria-labelledby="acc-button-mechanics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/physics/24/defining-energy/199">Defining Energy</a></li> <li><a href="/en/library/physics/24/waves-and-wave-motion/102">Waves and Wave Motion</a></li> <li><a href="/en/library/physics/24/gravity/118">Gravity</a></li> <li><a href="/en/library/physics/24/thermodynamics-i/200">Thermodynamics I</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-process-of-science" data-accordion="button" aria-controls="acc-panel-process-of-science" aria-expanded="false"> <span class="accordion__button__label"> Process of Science </span> </button> <div class="accordion__panel" id="acc-panel-process-of-science" data-accordion="panel" aria-labelledby="acc-button-process-of-science" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-introduction" data-accordion="button" aria-controls="acc-panel-introduction" aria-expanded="false"> <span class="accordion__button__label"> Introduction </span> </button> <div class="accordion__panel" id="acc-panel-introduction" data-accordion="panel" aria-labelledby="acc-button-introduction" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-process-of-science/176">The Process of Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-the-culture-of-science" data-accordion="button" aria-controls="acc-panel-the-culture-of-science" aria-expanded="false"> <span class="accordion__button__label"> The Culture of Science </span> </button> <div class="accordion__panel" id="acc-panel-the-culture-of-science" data-accordion="panel" aria-labelledby="acc-button-the-culture-of-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-nature-of-scientific-knowledge/185">The Nature of Scientific Knowledge</a></li> <li><a href="/en/library/process-of-science/49/scientists-and-the-scientific-community/172">Scientists and the Scientific Community</a></li> <li><a href="/en/library/process-of-science/49/scientific-ethics/161">Scientific Ethics</a></li> <li><a href="/en/library/process-of-science/49/scientific-institutions-and-societies/162">Scientific Institutions and Societies</a></li> </ul> </div> <button class="accordion__button" id="acc-button-ideas-in-science" data-accordion="button" aria-controls="acc-panel-ideas-in-science" aria-expanded="false"> <span class="accordion__button__label"> Ideas in Science </span> </button> <div class="accordion__panel" id="acc-panel-ideas-in-science" data-accordion="panel" aria-labelledby="acc-button-ideas-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/theories-hypotheses-and-laws/177">Theories, Hypotheses, and Laws</a></li> <li><a href="/en/library/process-of-science/49/scientific-controversy/181">Scientific Controversy</a></li> <li><a href="/en/library/process-of-science/49/creativity-in-science/182">Creativity in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-research-methods" data-accordion="button" aria-controls="acc-panel-research-methods" aria-expanded="false"> <span class="accordion__button__label"> Research Methods </span> </button> <div class="accordion__panel" id="acc-panel-research-methods" data-accordion="panel" aria-labelledby="acc-button-research-methods" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/the-practice-of-science/148">The Practice of Science</a></li> <li><a href="/en/library/process-of-science/49/experimentation-in-scientific-research/150">Experimentation in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/description-in-scientific-research/151">Description in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/comparison-in-scientific-research/152">Comparison in Scientific Research</a></li> <li><a href="/en/library/process-of-science/49/modeling-in-scientific-research/153">Modeling in Scientific Research</a></li> </ul> </div> <button class="accordion__button" id="acc-button-data" data-accordion="button" aria-controls="acc-panel-data" aria-expanded="false"> <span class="accordion__button__label"> Data </span> </button> <div class="accordion__panel" id="acc-panel-data" data-accordion="panel" aria-labelledby="acc-button-data" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/data-analysis-and-interpretation/154">Data Analysis and Interpretation</a></li> <li><a href="/en/library/process-of-science/49/uncertainty-error-and-confidence/157">Uncertainty, Error, and Confidence</a></li> <li><a href="/en/library/process-of-science/49/statistics-in-science/155">Statistics in Science</a></li> <li><a href="/en/library/process-of-science/49/using-graphs-and-visual-data-in-science/156">Using Graphs and Visual Data in Science</a></li> </ul> </div> <button class="accordion__button" id="acc-button-scientific-communication" data-accordion="button" aria-controls="acc-panel-scientific-communication" aria-expanded="false"> <span class="accordion__button__label"> Scientific Communication </span> </button> <div class="accordion__panel" id="acc-panel-scientific-communication" data-accordion="panel" aria-labelledby="acc-button-scientific-communication" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/process-of-science/49/understanding-scientific-journals-and-articles/158">Understanding Scientific Journals and Articles</a></li> <li><a href="/en/library/process-of-science/49/utilizing-the-scientific-literature/173">Utilizing the Scientific Literature</a></li> <li><a href="/en/library/process-of-science/49/peer-review-in-scientific-publishing/159">Peer Review in Scientific Publishing</a></li> <li><a href="/en/library/process-of-science/49/the-how-and-why-of-scientific-meetings/186">The How and Why of Scientific Meetings</a></li> </ul> </div> </div> </div> <button class="accordion__button" id="acc-button-scientists-and-research" data-accordion="button" aria-controls="acc-panel-scientists-and-research" aria-expanded="false"> <span class="accordion__button__label"> Scientists and Research </span> </button> <div class="accordion__panel" id="acc-panel-scientists-and-research" data-accordion="panel" aria-labelledby="acc-button-scientists-and-research" role="region"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-button-scientific-research" data-accordion="button" aria-controls="acc-panel-scientific-research" aria-expanded="false"> <span class="accordion__button__label"> Scientific Research </span> </button> <div class="accordion__panel" id="acc-panel-scientific-research" data-accordion="panel" aria-labelledby="acc-button-scientific-research" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/collaborative-research-in-the-arctic-towards-understanding-climate-change/183">Collaborative Research in the Arctic Towards Understanding Climate Change</a></li> <li><a href="/en/library/scientists-and-research/58/from-stable-chromosomes-to-jumping-genes/184">From Stable Chromosomes to Jumping Genes</a></li> <li><a href="/en/library/scientists-and-research/58/an-elegant-experiment-to-test-the-process-of-dna-replication/187">An Elegant Experiment to Test the Process of DNA Replication</a></li> <li><a href="/en/library/scientists-and-research/58/the-founding-of-neuroscience/233">The Founding of Neuroscience</a></li> <li><a href="/en/library/scientists-and-research/58/tracking-endangered-jaguars-across-the-border/189">Tracking Endangered Jaguars across the Border</a></li> <li><a href="/en/library/scientists-and-research/58/atmospheric-chemistry-research-that-changed-global-policy/211">Atmospheric Chemistry Research that Changed Global Policy</a></li> <li><a href="/en/library/scientists-and-research/58/revolutionizing-medicine-with-monoclonal-antibodies/220">Revolutionizing Medicine with Monoclonal Antibodies</a></li> <li><a href="/en/library/scientists-and-research/58/uncovering-the-mysteries-of-chronic-mountain-sickness/238">Uncovering the Mysteries of Chronic Mountain Sickness</a></li> </ul> </div> <button class="accordion__button" id="acc-button-profiles-in-science" data-accordion="button" aria-controls="acc-panel-profiles-in-science" aria-expanded="false"> <span class="accordion__button__label"> Profiles in Science </span> </button> <div class="accordion__panel" id="acc-panel-profiles-in-science" data-accordion="panel" aria-labelledby="acc-button-profiles-in-science" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/scientists-and-research/58/luis-e.-miramontes/232">Luis E. Miramontes</a></li> <li><a href="/en/library/scientists-and-research/58/bernardo-houssay/237">Bernardo Houssay</a></li> <li><a href="/en/library/scientists-and-research/58/craig-lee/256">Craig Lee</a></li> <li><a href="/en/library/scientists-and-research/58/david-ho/241">David Ho</a></li> <li><a href="/en/library/scientists-and-research/58/louis-tompkins-wright/244">Louis Tompkins Wright</a></li> <li><a href="/en/library/scientists-and-research/58/carlos-j.-finlay/217">Carlos J. Finlay</a></li> <li><a href="/en/library/scientists-and-research/58/cecilia-payne/290">Cecilia Payne</a></li> <li><a href="/en/library/scientists-and-research/58/jazmin-scarlett/291">Jazmin Scarlett</a></li> <li><a href="/en/library/scientists-and-research/58/ramari-stewart/292">Ramari Stewart</a></li> <li><a href="/en/library/scientists-and-research/58/johnson-cerda/300">Johnson Cerda</a></li> <li><a href="/en/library/scientists-and-research/58/ellen-ochoa/201">Ellen Ochoa</a></li> <li><a href="/en/library/scientists-and-research/58/ruth-benerito/205">Ruth Benerito</a></li> <li><a href="/en/library/scientists-and-research/58/franklin-chang-díaz/219">Franklin Chang Díaz</a></li> <li><a href="/en/library/scientists-and-research/58/percy-lavon-julian/221">Percy Lavon Julian</a></li> <li><a href="/en/library/scientists-and-research/58/luis-walter-alvarez/229">Luis Walter Alvarez</a></li> <li><a href="/en/library/scientists-and-research/58/france-anne-dominic-córdova/230">France Anne-Dominic Córdova</a></li> </ul> </div> </div> </div> </div> </div> </li> <li>  <button class="button" data-toggle="dropdown">Earth Science </button> <div class="nav__dropdown box-shadow-1 padding-1"> <div class="accordion accordion--secondary font-size-sm"> <div class="accordion accordion--secondary"> <button class="accordion__button" id="acc-sub-button-plate-tectonics" data-accordion="button" aria-controls="acc-sub-panel-plate-tectonics" aria-expanded="false"> <span class="accordion__button__label"> Plate Tectonics </span> </button> <div class="accordion__panel" id="acc-sub-panel-plate-tectonics" data-accordion="panel" aria-labelledby="acc-sub-button-plate-tectonics" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/origins-of-plate-tectonic-theory/65">Origins of Plate Tectonic Theory</a></li> <li><a href="/en/library/earth-science/6/plate-boundaries/66">Plate Boundaries</a></li> <li><a href="/en/library/earth-science/6/earth-structure/69">Earth Structure</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-earth-cycles" data-accordion="button" aria-controls="acc-sub-panel-earth-cycles" aria-expanded="false"> <span class="accordion__button__label"> Earth Cycles </span> </button> <div class="accordion__panel" id="acc-sub-panel-earth-cycles" data-accordion="panel" aria-labelledby="acc-sub-button-earth-cycles" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/the-rock-cycle/128">The Rock Cycle</a></li> <li><a href="/en/library/earth-science/6/the-hydrologic-cycle/99">The Hydrologic Cycle</a></li> <li><a href="/en/library/earth-science/6/the-carbon-cycle/95">The Carbon Cycle</a></li> <li><a href="/en/library/earth-science/6/the-nitrogen-cycle/98">The Nitrogen Cycle</a></li> <li><a href="/en/library/earth-science/6/the-phosphorus-cycle/197">The Phosphorus Cycle</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-rocks-and-minerals" data-accordion="button" aria-controls="acc-sub-panel-rocks-and-minerals" aria-expanded="false"> <span class="accordion__button__label"> Rocks and Minerals </span> </button> <div class="accordion__panel" id="acc-sub-panel-rocks-and-minerals" data-accordion="panel" aria-labelledby="acc-sub-button-rocks-and-minerals" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/defining-minerals/119">Defining Minerals</a></li> <li class="current">Identifying Minerals</li> <li><a href="/en/library/earth-science/6/the-silicate-minerals/140">The Silicate Minerals</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-atmosphere-and-oceans" data-accordion="button" aria-controls="acc-sub-panel-atmosphere-and-oceans" aria-expanded="false"> <span class="accordion__button__label"> Atmosphere and Oceans </span> </button> <div class="accordion__panel" 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href="/en/library/earth-science/6/circulation-in-the-atmosphere/255">Circulation in the Atmosphere</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-hazards" data-accordion="button" aria-controls="acc-sub-panel-hazards" aria-expanded="false"> <span class="accordion__button__label"> Hazards </span> </button> <div class="accordion__panel" id="acc-sub-panel-hazards" data-accordion="panel" aria-labelledby="acc-sub-button-hazards" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/natural-hazards-and-risk/288">Natural Hazards and Risk</a></li> </ul> </div> <button class="accordion__button" id="acc-sub-button-earth-history" data-accordion="button" aria-controls="acc-sub-panel-earth-history" aria-expanded="false"> <span class="accordion__button__label"> Earth History </span> </button> <div class="accordion__panel" id="acc-sub-panel-earth-history" data-accordion="panel" aria-labelledby="acc-sub-button-earth-history" role="region"> <ul class="nav text-color-link"> <li><a href="/en/library/earth-science/6/extinction/295">Extinction</a></li> <li><a href="/en/library/earth-science/6/mass-extinctions/294">Mass Extinctions</a></li> </ul> </div> </div> </div> </div> </li> </ul> </nav>  <div id="theTop"></div> <main id="skip-header-content"> <div class="margin-bottom-5"> <article class="container wide module"> <header class="grid grid--sidebar-right module__header"> <div class="module__header__title"> <span class="subcategory"> <strong><em>Rocks and Minerals</em></strong> </span> <h1>Identifying Minerals: <sub><em>Characterizing minerals' physical properties</em></sub></h1> <p class="byline">by Anne E. Egger, Ph.D.</p> <nav class="module__header__tabs"> <ul class="tabs-nav tabs-nav--horizontal library"> <li> <a href="/en/library/earth-science/6/identifying-minerals/130/reading" aria-current="page" >Reading</a> </li> <li> <a href="/en/library/earth-science/6/identifying-minerals/130/quiz">Quiz</a> </li> <li> <a href="/en/library/earth-science/6/identifying-minerals/130/resources">Teach with this</a> </li> </ul> </nav> </div> <script type="application/ld+json"> { "@context": "http://schema.org", "@type": "AudioObject", "contentUrl": "https://www.visionlearning.com/img/library/moduleAudio/module_130.mp3", "description": "Recording of Identifying Minerals : Minerals are classified on the basis of their chemical composition, which is expressed in their physical properties. This module, the second in a series on minerals, describes the physical properties that are commonly used to identify minerals. These include color, crystal form, hardness, density, luster, and cleavage.", "encodingFormat": "mp3", "name": "module_130.mp3" } </script> <div class="module_header_audio"> <div class="audio-player border border-radius"> <audio id="audio"> <source src="https://www.visionlearning.com/img/library/moduleAudio/module_130.mp3" type="audio/mpeg"> Your browser does not support the audio element. </audio> <div class="audio-player__title"> <p>Listen to this reading</p> <span class="audio-player__timestamp" id="timestamp"> 00:00 </span> </div> <div class="audio-player__controls" id="controls"> <button class="button button--icon-only" id="play-pause-button"> <span class="icon icon-play" aria-hidden="true"></span> </button> <div class="audio-player__progress" id="progress-bar" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="0" aria-label="Use arrow keys to forward or rewind the audio" role="slider"> <div class="audio-player__progress__fill"> <span class="audio-player__thumb"></span> </div> </div> <div class="audio-player__volume-container"> <button id="mute-button"> <span class="icon icon-volume"></span> </button> <div class="audio-player__volume" tabindex="0" aria-valuemin="0" aria-valuemax="100" aria-valuenow="100" aria-label="Use arrow keys to adjust volume" role="slider"> <div class="audio-player__volume__fill"> <span class="audio-player__thumb"></span> </div> </div> </div> </div> </div> </div> </header> <hr class="divider"/>   <div class="grid grid--sidebar-right grid--divider"> <div class="order-2 order-1--lg module__main"> <div class="narrow margin-x-auto margin-y-5"> <div class="accordion margin-bottom-5">  <button class="accordion__button" id="acc-button-key-concepts" data-accordion="button" aria-controls="acc-panel-key-concepts" aria-expanded="true" tabindex="0"> Did you know? </button> <div class="accordion__panel shown show" id="acc-panel-key-concepts" data-accordion="panel" aria-labelledby="acc-button-key-concepts" role="region"> <div class="accordion__panel__content"> <p>Did you know that even though thousands of minerals have been named, only about a dozen are common in the Earth’s crust? Sophisticated laboratory equipment exists for determining the exact chemical composition of minerals, yet sometimes the most essential tools in geology are a magnifying lens and a penknife. Using just these tools, scientists can identify about 90% of what they encounter in the field.</p> </div> </div>  <button class="accordion__button" id="acc-button-table-of-contents" data-accordion="button" aria-controls="acc-panel-table-of-contents" aria-expanded="false" tabindex="0"> Key concepts </button> <div class="accordion__panel" id="acc-panel-table-of-contents" data-accordion="panel" aria-labelledby="acc-button-table-of-contents" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <ul class="bulleted"> <li><p>Properties that help geologists identify a mineral in a rock are: color, hardness, luster, crystal forms, density, and cleavage.</p></li> <li><p>Crystal form, cleavage, and hardness are determined primarily by the crystal structure at the atomic level.</p></li> <li><p>Color and density are determined primarily by the chemical composition.</p></li> <li><p>Minerals are classified on the basis of their chemical composition.</p></li> </ul> </div> </div>  <button class="accordion__button" id="acc-button-terms-you-should-know" data-accordion="button" aria-controls="acc-panel-terms-you-should-know" aria-expanded="false" tabindex="0"> Terms you should know </button> <div class="accordion__panel" id="acc-panel-terms-you-should-know" data-accordion="panel" aria-labelledby="acc-button-terms-you-should-know" role="region" aria-hidden="true"> <div class="accordion__panel__content"> <dl> <dt><a href="/en/glossary/view/luster">luster </a></dt> <dd> the way an object reflects light; sheen, gloss </dd> <dt>ore </dt> <dd> rock from which a valuable product such as a metal can be extracted </dd> <dt><a href="/en/glossary/view/quartz">quartz </a></dt> <dd> a common mineral made of silicon and oxygen </dd> <dt><a href="/en/glossary/view/rover">rover </a></dt> <dd> a vehicle used for exploring remote regions</dd> </dl> </div> </div> </div> <hr class="border-color-dark" /> <section> <div class="container narrow"> <p><mark id="ngss-362" class="ngss">Geologists have recently determined that the <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">minerals</mark> goethite and hematite exist in abundance on Mars, sure signs of the presence of water (see Figure 1 for a picture). None of those geologists have been to Mars, of course, but the unmanned <mark class="term" data-term="rover" data-term-def="A vehicle used for exploring the surface of the moon or a planet." data-term-url="/en/glossary/view/rover/8525">rovers</mark> Spirit and Opportunity have. These rovers are equipped with three <mark class="term" data-term="mass" data-term-def="A fundamental property of matter which is a numerical measure of the inertia of an object or the amount of matter&hellip;" data-term-url="/en/glossary/view/mass/3417">mass</mark> <mark class="term" data-term="spectrometer" data-term-def="An instrument that measures the intensity of radiation, including light, as a function of its wavelength. Because different substances, including elements&hellip;" data-term-url="/en/glossary/view/spectrometer/2380">spectrometers</mark>, each of which is capable of determining the chemical composition of a <mark class="term" data-term="solid" data-term-def="A collection of atoms or molecules that are held together so that, under constant conditions, they maintain a defined shape and&hellip;" data-term-url="/en/glossary/view/solid/7571">solid</mark> with a high degree of <mark class="term" data-term="accuracy" data-term-def="In science, the term accuracy describes how well a measurement approximates the theoretically correct value of that measurement, for example, how&hellip;" data-term-url="/en/glossary/view/accuracy/4222">accuracy</mark>. With such a precise chemical <mark class="term" data-term="analysis" data-term-def="The careful study of data to look for patterns." data-term-url="/en/glossary/view/analysis/8553">analysis</mark> in hand, geologists on Earth had no problem identifying the minerals.</mark></p> <div class="figure"><figure> <a href="/images/figure-images/130-a-2x.jpg" title="<strong>Figure 1:</strong> The small spheres in this picture were dubbed “berries” by geologists who first saw them. They sit on the surface of Mars and were photographed by the Mars rover Opportunity. A mass spectrometer on the rover was able to determine the chemical content of the berries and geologists recognized the chemical formula for hematite (Fe2O3)."> <span class="fa fa-search-plus"></span> <img src="/images/figure-images/130-a.jpg" alt="The small spheres in this picture were dubbed “berries” by geologists who first saw them."> </a> <figcaption><strong>Figure 1:</strong> The small spheres in this picture were dubbed “berries” by geologists who first saw them. They sit on the surface of Mars and were photographed by the Mars rover Opportunity. A mass spectrometer on the rover was able to determine the chemical content of the berries and geologists recognized the chemical formula for hematite (Fe2O3).<span class="credit">© NASA/JPL/Cornell</span></figcaption> </figure></div><p>A <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">mineral</mark> is defined in part by a specific chemical composition. In <mark class="term" data-term="theory" data-term-def="A scientific theory is an explanation inferred from multiple lines of evidence for some broad aspect of the natural world and&hellip;" data-term-url="/en/glossary/view/theory/4854">theory</mark>, therefore, it is always easy to identify a mineral, if you can determine the chemical composition with a <mark class="term" data-term="mass" data-term-def="A fundamental property of matter which is a numerical measure of the inertia of an object or the amount of matter&hellip;" data-term-url="/en/glossary/view/mass/3417">mass</mark> <mark class="term" data-term="mass spectrometer" data-term-url="/en/glossary/view/mass+spectrometer" data-term-def="A spectrometer that measures the composition of samples by analyzing the mass to charge ratio (m/z) of components in the sample.&hellip;">spectrometer</mark> like the Mars <mark class="term" data-term="rover" data-term-def="A vehicle used for exploring the surface of the moon or a planet." data-term-url="/en/glossary/view/rover/8525">rovers</mark>. In reality, however, even if you are looking at rocks on Earth, determining the exact chemical composition of a substance involves significant time preparing the sample and sophisticated laboratory equipment (and often significant money). Luckily, it is usually unnecessary to go to such lengths, because there are much easier ways that require little more than a magnifying lens and a penknife. </p> <p><section id="toc_1" class=""> <h2>Identifying minerals by physical properties</h2></p> <p>The most common minerals in Earth's <mark class="term" data-term="crust" data-term-def="The uppermost 5-70 km of the Earth. There are two types of crust: continental and oceanic. Continental crust ranges from 10-70&hellip;" data-term-url="/en/glossary/view/crust/880">crust</mark> can often be identified in the field using basic physical properties such as color, shape, and hardness. The context of a mineral is important, too – some <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">minerals</mark> can form under the same conditions, so you are likely to find them in the same rock, while others form under very different conditions and will never occur in the same rock. For this reason, context (the other surrounding minerals and type of rock) can often be used to rule out minerals that have similar color, for example. Although there are many thousands of named minerals, only a dozen or so are common in Earth's crust. Testing a few physical properties therefore means that you can identify about 90% of what you are likely to encounter in the field.</p><p><mark id="ngss-363" class="ngss">Because the physical properties of a <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">mineral</mark> are determined by its chemical composition and internal atomic structure, they can be used diagnostically,</mark> the way a runny nose and sore throat can be used to diagnose a cold. <mark id="ngss-364" class="ngss">There are many physical properties of minerals that are testable with varying degrees of ease, including color, <mark class="term" data-term="crystal" data-term-def="A solid of defined shape that is bound by plane surfaces (facets) that intersect at characteristic angles. The shape of a&hellip;" data-term-url="/en/glossary/view/crystal/1564">crystal</mark> form (or shape), hardness, <mark class="term" data-term="luster" data-term-def="The way an object reflects light; sheen, gloss." data-term-url="/en/glossary/view/luster/8523">luster</mark> (or shine), <mark class="term" data-term="density" data-term-def="A measure of the compactness of a substance given by the mass per unit volume (d = m/v). Common units of&hellip;" data-term-url="/en/glossary/view/density/863">density</mark>, and <mark class="term" data-term="cleavage" data-term-def="Breakage in crystal structure of certain minerals along planes where atomic bonds are weakest." data-term-url="/en/glossary/view/cleavage/8526">cleavage</mark> or fracture (how the mineral breaks). In addition, many minerals have unique properties, such as <mark class="term" data-term="radioactivity" data-term-def="The spontaneous emission of radiation, due to a nuclear reaction or direct emission from an unstable atomic nucleus. Radioactivity takes&hellip;" data-term-url="/en/glossary/view/radioactivity/5301">radioactivity</mark>, <mark class="term" data-term="fluorescence" data-term-def="The emission of light by a substance following the absorption of light or other energy by the substance. The emitted light&hellip;" data-term-url="/en/glossary/view/fluorescence/9255">fluorescence</mark> under black light, or <mark class="term" data-term="reaction" data-term-def="A chemical change when substances come into contact with each other." data-term-url="/en/glossary/view/reaction/8263">reaction</mark> to <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark>. In most cases, it is necessary to observe a few properties to identify a mineral;</mark> to extend the medical analogy even further, a runny nose is a symptom of a cold <mark class="term" data-term="virus" data-term-def="An ultramicroscopic infectious agent that can only replicate within the cells of living hosts, mainly bacteria, plants, and animals. Viruses have&hellip;" data-term-url="/en/glossary/view/virus/5302">virus</mark>, allergies, or a sinus infection among other things, so we have to use other symptoms to diagnose the problem – a headache, fever, watery eyes, and so on.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6439"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">The context in which a mineral is found</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6439-0-option-a" name="quiz-option-6439" type="radio" value="can be useful in identifying the mineral." > <span class="option__label"> <span class="screen-reader-only">a.</span> can be useful in identifying the mineral. </span> </label> <span class="quiz__response" id="response-6439-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6439-1-option-b" name="quiz-option-6439" type="radio" value="has little to do with identifying the mineral." > <span class="option__label"> <span class="screen-reader-only">b.</span> has little to do with identifying the mineral. </span> </label> <span class="quiz__response" id="response-6439-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc2_1"><h3>Color</h3><p>The most obvious <mark class="term" data-term="property" data-term-def="A characteristic or attribute." data-term-url="/en/glossary/view/property/8555">property</mark> of a mineral, its color, is unfortunately also the least diagnostic. In the same way that a headache is a symptom for a whole host of problems from the flu to a head injury, many minerals share the same color. For example, several minerals are green in color – olivine, epidote, and actinolite, just to name a few. On the other extreme, one mineral can take on several different colors if there are impurities in the chemical composition, such as <mark class="term" data-term="quartz" data-term-def="A common mineral compound made of silica." data-term-url="/en/glossary/view/quartz/8524">quartz</mark>, which can be clear, smoky, pink, purple, or yellow.</p><p>Part of the reason that the color of minerals is not uniquely diagnostic is that there are several components of the <mark class="term" data-term="crystal" data-term-def="A solid of defined shape that is bound by plane surfaces (facets) that intersect at characteristic angles. The shape of a&hellip;" data-term-url="/en/glossary/view/crystal/1564">crystal</mark> compositions and structure that can produce color. The presence of some <mark class="term" data-term="element" data-term-def="One of fewer than 118 pure chemical substances. An element is a substance composed of atoms with identical atomic number." data-term-url="/en/glossary/view/element/1510">elements</mark>, such as iron, always results in a colored mineral, but iron can produce a wide variety of colors depending on its state of oxidation – black, red, or green, most commonly. Some minerals have color-producing elements in their crystal structure, like olivine (Fe<sub>2</sub>SiO<sub>4</sub>), while others incorporate them as impurities, like <mark class="term" data-term="quartz" data-term-def="A common mineral compound made of silica." data-term-url="/en/glossary/view/quartz/8524">quartz</mark> (SiO<sub>2</sub>). All of this variability makes it difficult to solely use color to identify a mineral. However, in combination with other properties such as crystal form, color can help narrow the possibilities. As an example, hornblende, biotite, and muscovite are all very commonly found in rocks such as <mark class="term" data-term="granite" data-term-def="A light-colored, coarse-grained igneous rock formed by cooling of silica-rich magma below the surface of the Earth. Granite is considered to&hellip;" data-term-url="/en/glossary/view/granite/1665">granite</mark>. Hornblende and biotite are both black, but they can be easily distinguished by their crystal form because biotite occurs in sheets, while hornblende forms stout prisms (Figure 2). Muscovite and biotite both form in sheets, but they are different colors – muscovite is colorless, in fact.</p><div class="figure"><figure> <a href="/images/figure-images/130-b-2x.jpg" title="<strong>Figure 2:</strong> These three minerals can be distinguished using both color and form. Biotite and hornblende share the same color, but are different forms; muscovite and biotite share form but not color."> <span class="fa fa-search-plus"></span> <img src="/images/figure-images/130-b.jpg" alt="Biotite, hornblende, and muscovite"> </a> <figcaption><strong>Figure 2:</strong> These three minerals can be distinguished using both color and form. Hornblende (left) and biotite (middle) share the same color, but are different forms; muscovite (right) and biotite share form but not color. </figcaption> </figure></div> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6438"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Color is one of the best ways to identify a mineral.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6438-0-option-a" name="quiz-option-6438" type="radio" value="true" > <span class="option__label"> <span class="screen-reader-only">a.</span> true </span> </label> <span class="quiz__response" id="response-6438-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6438-1-option-b" name="quiz-option-6438" type="radio" value="false" > <span class="option__label"> <span class="screen-reader-only">b.</span> false </span> </label> <span class="quiz__response" id="response-6438-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc2_2"><h3>Crystal form</h3><p><mark id="ngss-365" class="ngss">The external shape of a mineral crystal (or its crystal form) is determined largely by its internal atomic structure,</mark> which means that this <mark class="term" data-term="property" data-term-def="A characteristic or attribute." data-term-url="/en/glossary/view/property/8555">property</mark> can be highly diagnostic. Specifically, the form of a <mark class="term" data-term="crystal" data-term-def="A solid of defined shape that is bound by plane surfaces (facets) that intersect at characteristic angles. The shape of a&hellip;" data-term-url="/en/glossary/view/crystal/1564">crystal</mark> is defined by the angular relationships between crystal faces (recall Steno's <mark class="term" data-term="law" data-term-def="In science, a principle that describes a phenomenon, often mathematically." data-term-url="/en/glossary/view/law/8686">Law</mark> of Interfacial Angles as discussed in our <a href="/library/module_viewer.php?mid=119#steno">Minerals I</a> module). Some minerals, like halite (NaCl, or salt) and pyrite (FeS) have a cubic form (see Figure 3, left); others like tourmaline (see Figure 3, middle) are prismatic. Some <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">minerals</mark>, like azurite and malachite, which are both copper ores, don't form regular crystals, and are <mark class="term" data-term="amorphous" data-term-def="Having no specific arrangement or organization. Amorphous solids are those that have no specific arrangement of atoms and usually melt over&hellip;" data-term-url="/en/glossary/view/amorphous/7473">amorphous</mark> (Figure 3).</p><div class="figure"><figure> <a href="/images/figure-images/130-c-2x.jpg" title="<strong>Figure 3:</strong> Examples of different types of crystal forms. On the left, pyrite has a cubic form; tourmaline (middle) is prismatic; azurite and malachite (on the right) are often amorphous."> <span class="fa fa-search-plus"></span> <img src="/images/figure-images/130-c.jpg" alt="Pyrite, tourmaline, and azurite"> </a> <figcaption><strong>Figure 3:</strong> Examples of different types of crystal forms. On the left, pyrite has a cubic form; tourmaline (middle) is prismatic; azurite and malachite (on the right) are often amorphous.</figcaption> </figure></div><p>Unfortunately, we don't always get to see the crystal form. We see perfect <mark class="term" data-term="crystal" data-term-def="A solid of defined shape that is bound by plane surfaces (facets) that intersect at characteristic angles. The shape of a&hellip;" data-term-url="/en/glossary/view/crystal/1564">crystals</mark> only when they have had a chance to grow into a cavity, such as in a geode. When crystals grow in the context of cooling <mark class="term" data-term="magma" data-term-def="Molten rock below the surface of the Earth." data-term-url="/en/glossary/view/magma/869">magma</mark>, however, they are competing for space with all of the other crystals that are trying to grow and they tend to fill in whatever space they can. The shape of the crystal can vary quite a bit depending on the amount of space available, but the angle between the crystal faces will always be the same.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6437"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">Which is more helpful in identifying a mineral?</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6437-0-option-a" name="quiz-option-6437" type="radio" value="The shape of its crystals." > <span class="option__label"> <span class="screen-reader-only">a.</span> The shape of its crystals. </span> </label> <span class="quiz__response" id="response-6437-0"> <strong>Incorrect.</strong> </span> </div> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6437-1-option-b" name="quiz-option-6437" type="radio" value="The angle between its crystal faces." > <span class="option__label"> <span class="screen-reader-only">b.</span> The angle between its crystal faces. </span> </label> <span class="quiz__response" id="response-6437-1"> <strong>Correct!</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc2_3"><h3>Hardness</h3><p><mark id="ngss-366" class="ngss">The hardness of a <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">mineral</mark> can be tested in several ways. Most commonly, minerals are compared to an object of known hardness using a scratch <mark class="term" data-term="Test" data-term-def="This is a test glossary term." data-term-url="/en/glossary/view/Test/12984">test</mark> – if a nail, for example, can scratch a crystal, than the nail is harder than that mineral. In the early 1800s, <mark class="term" data-term="Friedrich Mohs" data-term-def="German geologist and mineralogist born in Gernrode (1773-1839). In 1802, after studying at the Mining Academy in Freiberg, Saxony, Mohs moved&hellip;" data-term-url="/en/glossary/view/Mohs%2C+Friedrich/4535">Friedrich Mohs</mark>, an Austrian mineralogist, developed a relative hardness <mark class="term" data-term="scale" data-term-def="An instrument for measuring heat energy or weight in which units are marked at intervals; a system for quantifying heat energy&hellip;" data-term-url="/en/glossary/view/scale/8536">scale</mark> based on the scratch test. He assigned integer numbers to each mineral, where 1 is the softest and 10 is the hardest.</mark> This scale is shown in Figure 4.</p><div class="figure"><figure> <a href="/images/figure-images/130-d-2x.jpg" title="<strong>Figure 4:</strong> Mohs' scale of mineral hardness, where 1 is the softest and 10 is the hardest."> <span class="fa fa-search-plus"></span> <img src="/images/figure-images/130-d.jpg" alt="Mohs' scale of mineral hardness"> </a> <figcaption><strong>Figure 4:</strong> Mohs' scale of mineral hardness, where 1 is the softest and 10 is the hardest.</figcaption> </figure></div><p>The scale is not linear (corundum is actually 4 times as hard as quartz), and other <mark class="term" data-term="method" data-term-def="A procedure or process; a systematic way of performing a task or conducting research." data-term-url="/en/glossary/view/method/8238">methods</mark> have now provided more rigorous measurements of hardness. <mark id="ngss-367" class="ngss">Despite the lack of <mark class="term" data-term="precision" data-term-def="In science, precision refers to the degree of specified detail which can be expressed in a value. For example, a value&hellip;" data-term-url="/en/glossary/view/precision/4223">precision</mark> in the Mohs <mark class="term" data-term="scale" data-term-def="An instrument for measuring heat energy or weight in which units are marked at intervals; a system for quantifying heat energy&hellip;" data-term-url="/en/glossary/view/scale/8536">scale</mark>, it remains useful because it is simple, easy to remember, and easy to <mark class="term" data-term="Test" data-term-def="This is a test glossary term." data-term-url="/en/glossary/view/Test/12984">test</mark>. The steel of a pocketknife (a common tool for geologists to carry in the field) falls almost right in the middle, so it is easy to distinguish the upper half from the lower half. For example, <mark class="term" data-term="quartz" data-term-def="A common mineral compound made of silica." data-term-url="/en/glossary/view/quartz/8524">quartz</mark> and calcite can look exactly the same – both are colorless and translucent, and occur in a wide variety of rocks. But a simple scratch test can tell them apart; calcite will be scratched by a pocketknife or rock hammer and quartz will not. Gypsum can also look a lot like calcite, but is so soft that it can be scratched by a fingernail.</mark></p><p>Variations in hardness make <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">minerals</mark> useful for different purposes. The softness of calcite makes it a popular material for sculpture (marble is made up entirely of calcite), whereas the hardness of diamond means that it is used as an abrasive to polish rock.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6436"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">The hardness of a mineral can be determined by attempting to scratch it with a knife.</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6436-0-option-a" name="quiz-option-6436" type="radio" value="true" > <span class="option__label"> <span class="screen-reader-only">a.</span> true </span> </label> <span class="quiz__response" id="response-6436-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6436-1-option-b" name="quiz-option-6436" type="radio" value="false" > <span class="option__label"> <span class="screen-reader-only">b.</span> false </span> </label> <span class="quiz__response" id="response-6436-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc2_4"><h3>Luster</h3><p><mark id="ngss-368" class="ngss">The <mark class="term" data-term="luster" data-term-def="The way an object reflects light; sheen, gloss." data-term-url="/en/glossary/view/luster/8523">luster</mark> of a <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">mineral</mark> is the way that it <mark class="term" data-term="reflect" data-term-def="To change direction in response to hitting a surface; to bounce off in a different direction." data-term-url="/en/glossary/view/reflect/8276">reflects</mark> <mark class="term" data-term="light" data-term-def="A form of electromagnetic radiation. Visible light is that associated with stimulating the organs of sight, which for normal human&hellip;" data-term-url="/en/glossary/view/light/1498">light</mark>. This may seem like a difficult distinction to make, but picture the difference between the way light reflects off a glass window and the way it reflects off of a shiny chrome car bumper.</mark> A mineral that reflects light the way glass does has a vitreous (or glassy) luster; a mineral that reflects light like chrome has a metallic luster. There are a variety of additional possibilities for luster, including pearly, waxy, and resinous (see pictures in Figure 5). Minerals that are as brilliantly reflective as diamond have an adamantine luster. With a little practice, luster is as easily recognized as color and can be quite distinctive, particularly for minerals that occur in multiple colors like <mark class="term" data-term="quartz" data-term-def="A common mineral compound made of silica." data-term-url="/en/glossary/view/quartz/8524">quartz</mark>.</p><div class="figure"><figure> <a href="/images/figure-images/130-e-2x.jpg" title="<strong>Figure 5:</strong> Examples of only a few of the different lusters that can be seen in minerals. Galena (left) has a metallic luster, amber (middle) is resinous, and quartz (right) is glassy."> <span class="fa fa-search-plus"></span> <img src="/images/figure-images/130-e.jpg" alt="placeholder"> </a> <figcaption><strong>Figure 5:</strong> Examples of only a few of the different lusters that can be seen in minerals. Galena (left) has a metallic luster, amber (middle) is resinous, and quartz (right) is glassy.</figcaption> </figure></div></section> <section id="toc2_5"><h3>Density</h3><p><mark id="ngss-369" class="ngss">The <mark class="term" data-term="density" data-term-def="A measure of the compactness of a substance given by the mass per unit volume (d = m/v). Common units of&hellip;" data-term-url="/en/glossary/view/density/863">density</mark> of <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">minerals</mark> varies widely from about 1.01 g/cm<sup>3</sup> to about 17.5 g/cm<sup>3</sup>. The density of water is 1 g/cm<sup>3</sup>, pure iron has a density of 7.6 g/cm<sup>3</sup>, pure gold, 17.65 g/cm<sup>3</sup>.</mark> Minerals, therefore, occupy the range of densities between water and pure gold. Measuring the density of a specific mineral requires time-consuming techniques, and most geologists have developed a more intuitive sense for what is "normal" density, what is unusually heavy for its size, and what is unusually light. By "hefting" a rock, experienced geologists can usually guess if the rock is made up of minerals that contain iron or lead, for example, because it feels heavier than an <mark class="term" data-term="average" data-term-def="In statistics, average commonly refers to the arithmetic mean, also called simply "mean," which is one measure of the mid-point of&hellip;" data-term-url="/en/glossary/view/average/8542">average</mark> rock of the same size (see our <a href="/library/module_viewer.php?mid=37">Density </a> module for more information).</p></section> <section id="toc2_6"><h3>Cleavage and fracture</h3><p><mark id="ngss-370" class="ngss">Most <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">minerals</mark> contain <mark class="term" data-term="inherent" data-term-def="Part of the fundamental nature of something; belonging as an inseparable characteristic." data-term-url="/en/glossary/view/inherent/8253">inherent</mark> weaknesses within their atomic structures, a plane along which the <mark class="term" data-term="bond" data-term-def="The force that holds together units such as atoms or molecules. <br> <b>[verb]</b> To hold or fasten units such as atoms or molecules together." data-term-url="/en/glossary/view/bond/8297">bond</mark> strength is lower than the surrounding bonds. When hit with a hammer or otherwise broken, a mineral will tend to break along that plane of pre-existing weakness. This type of breakage is called <mark class="term" data-term="cleavage" data-term-def="Breakage in crystal structure of certain minerals along planes where atomic bonds are weakest." data-term-url="/en/glossary/view/cleavage/8526">cleavage</mark>, and the quality of the cleavage varies with the strength of the bonds.</mark> Biotite, for example, has layers of extremely weak <mark class="term" data-term="hydrogen bond" data-term-def="A strong dipole-dipole attraction between two or more molecules, at least one of which has a hydrogen atom bonded to an&hellip;" data-term-url="/en/glossary/view/hydrogen+bond/1560">hydrogen bonds</mark> that break very easily, thus biotite breaks along flat planes and is considered to have perfect cleavage (see Figure 6). Other minerals cleave along planar <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surfaces</mark> of varying roughness – these are considered to have good to poor cleavage.</p><div class="figure"><figure> <a href="/images/figure-images/130-f-2x.jpg" title="<strong>Figure 6:</strong> Several conchoidal fractures are visible in the mineral samples above. Note the concave surface and the curved ribs."> <span class="fa fa-search-plus"></span> <img src="/images/figure-images/130-f.jpg" alt="placeholder"> </a> <figcaption><strong>Figure 6:</strong> Several conchoidal fractures are visible in the mineral samples above. Note the concave surface and the curved ribs.</figcaption> </figure></div><p>Some <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">minerals</mark> don't have any planes of weakness in their atomic structure. These minerals don't have any <mark class="term" data-term="cleavage" data-term-def="Breakage in crystal structure of certain minerals along planes where atomic bonds are weakest." data-term-url="/en/glossary/view/cleavage/8526">cleavage</mark>, and instead they fracture. <mark class="term" data-term="quartz" data-term-def="A common mineral compound made of silica." data-term-url="/en/glossary/view/quartz/8524">Quartz</mark> fractures in a distinctive fashion, called conchoidal, which produces a concave <mark class="term" data-term="surface" data-term-def="The outside or external part; the topside face of something." data-term-url="/en/glossary/view/surface/8275">surface</mark> with a series of arcuate ribs similar to the way that glass fractures (see Figure 6). For quartz, in fact, this <em>lack</em> of cleavage is a distinguishing <mark class="term" data-term="property" data-term-def="A characteristic or attribute." data-term-url="/en/glossary/view/property/8555">property</mark>.</p> <div class="comprehension-checkpoint margin-y-4"> <h6 class="comprehension-checkpoint__header"> <span> <span class="icon icon-question"></span> </span> Comprehension Checkpoint </h6> <form class="" name="cc6435"> <div class="form-entry"> <div class="form-entry__field"> <span class="form-entry__field__label">A mineral with perfect cleavage</span> <div class="form-entry__option"> <div class="form-entry__option__radio" data-answer="correct"> <label> <input id="q1-6435-0-option-a" name="quiz-option-6435" type="radio" value="breaks along flat lines." > <span class="option__label"> <span class="screen-reader-only">a.</span> breaks along flat lines. </span> </label> <span class="quiz__response" id="response-6435-0"> <strong>Correct!</strong> </span> </div> <div class="form-entry__option__radio" data-answer="incorrect"> <label> <input id="q1-6435-1-option-b" name="quiz-option-6435" type="radio" value="does not break." > <span class="option__label"> <span class="screen-reader-only">b.</span> does not break. </span> </label> <span class="quiz__response" id="response-6435-1"> <strong>Incorrect.</strong> </span> </div> </div> </div> </div> </form> </div> </section> <section id="toc2_7"><h3>Mineral classification systems</h3><p>Physical properties provided the main basis for <mark class="term" data-term="classification" data-term-def="In biology, the arranging of groups of organisms into sets or divisions on the basis of their evolutionary relationships." data-term-url="/en/glossary/view/classification/879">classification</mark> of <mark class="term" data-term="mineral" data-term-def="A naturally formed, inorganic solid with a specific chemical composition and characteristic crystal structure. Examples of minerals include quartz (SiO<sub>2</sub>), salt&hellip;" data-term-url="/en/glossary/view/mineral/2978">minerals</mark> from the <mark class="term" data-term="Middle Ages" data-term-def="European history from the 5th century to the 15th century. The Middle Ages follow the fall of the Western Roman Empire&hellip;" data-term-url="/en/glossary/view/Middle+Ages/5329">Middle Ages</mark> through the mid-1800s. <mark id="ngss-371" class="ngss">Minerals were grouped according to characteristics such as hardness, so that diamond and corundum would be in the same class of minerals. As the ability to determine the chemical composition of minerals developed, so did a new classification <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>.</mark> Many scientists contributed to the discovery of mineral chemical <mark class="term" data-term="formula" data-term-def="An expression of the composition of a chemical compound using symbols." data-term-url="/en/glossary/view/formula/8554">formulas</mark>, but <mark class="term" data-term="James Dwight Dana" data-term-def="American geologist, mineralogist, and naturalist, born in Utica, New York (1813-1895). Dana published A System of Mineralogy in 1837, which remains&hellip;" data-term-url="/en/glossary/view/Dana%2C+James+Dwight/4565">James Dwight Dana</mark>, a mineralogist at Yale University from 1850 to 1892 (see Biography link in the Resources section), developed a classification system for minerals based on chemical composition that has survived to the present day. He grouped minerals according to their <mark class="term" data-term="anion" data-term-def="A negatively charged ion that migrates to the anode in an electrical cell." data-term-url="/en/glossary/view/anion/1522">anions</mark>, such as oxides (compounds with O<sup>2-</sup>), silicates (compounds with (SiO<sub>4</sub>)<sup>4-</sup>), and sulfates (compounds with (SO<sub>4</sub>)<sup>2-</sup>). <mark id="ngss-372" class="ngss">A chemical classification system meant that minerals that were grouped together theoretically also tended to appear with each other in rocks since they tended to develop under similar geochemical conditions.</mark></p><p>Physical properties still provide the main means for identification of minerals, however, though they are no longer used to group minerals (from the example above, corundum is an oxide while diamond is a pure <mark class="term" data-term="element" data-term-def="One of fewer than 118 pure chemical substances. An element is a substance composed of atoms with identical atomic number." data-term-url="/en/glossary/view/element/1510">element</mark>, so by Dana's <mark class="term" data-term="system" data-term-def="A group of interacting, interrelated or interdependent components that form a complex whole. The size of the system is defined for&hellip;" data-term-url="/en/glossary/view/system/3904">system</mark>, they are in separate groups). A composition-based grouping highlights some common mineral associations that allow geologists to make educated guesses about which minerals are present in a rock, even with only a quick glance. By far, the most common minerals are the silicates, which make up 90% of Earth's <mark class="term" data-term="crust" data-term-def="The uppermost 5-70 km of the Earth. There are two types of crust: continental and oceanic. Continental crust ranges from 10-70&hellip;" data-term-url="/en/glossary/view/crust/880">crust</mark>. Of the many hundreds of named silicate minerals, only about eight are common, one of which is <mark class="term" data-term="quartz" data-term-def="A common mineral compound made of silica." data-term-url="/en/glossary/view/quartz/8524">quartz</mark>. <mark id="ngss-373" class="ngss">The uncommon minerals are critical, however, as they include economically important ones such as galena, which is the primary ore for lead, and apatite, a phosphate mined for phosphoric <mark class="term" data-term="acid" data-term-def="Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different&hellip;" data-term-url="/en/glossary/view/acid/1573">acid</mark> that is added to fertilizers.</mark> <mark id="ngss-374" class="ngss">The discovery of new ore deposits depends on the ability of geologists to identify what they see in the field and recognize unusual mineral occurrences that should be explored in more detail in the laboratory. A hand lens, a pocketknife, and a lot of practice still provide the easiest and cheapest methods of identifying minerals.</mark></p> </div> </section> <hr class="border-color-dark" /> <footer class="module__footer"> <p class="citation"> <em> Anne E. Egger, Ph.D. “Identifying Minerals” Visionlearning Vol. EAS-2 (8), 2005. </em> </p>  <div class="title-list" name="further"> <p class="h6 title-list__title"> Further Reading </p> <ul class="grid grid--column-2--md grid--column-3--md gap-1"> <li> <a class="no-hover-focus height-100" href="/en/library/Earth-Science/6/Defining-Minerals/119"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_119-23061209065734.jpeg" alt="Defining Minerals"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> Defining Minerals: <em>Composition and crystal structure</em> </h2> </div> </article> </a> </li> <li> <a class="no-hover-focus height-100" href="/en/library/Earth-Science/6/The-Silicate-Minerals/140"> <article class="flex-row align-items-center flex-column--md align-items-start--md height-100 theme-light padding-2 gap-2"> <div class="width-30 width-auto--md"> <img class="border-radius box-shadow-1" src="/img/library/moduleImages/featured_image_140-23061209065801.jpg" alt="The Silicate Minerals"> </div> <div class="flex-grow-shrink"> <h2 class="h6 font-weight-normal"> The Silicate Minerals: <em>The silica tetrahedron and Earth's most common minerals</em> </h2> </div> </article> </a> </li> </ul> </div> </footer> </div>   </div>  <div class="order-1 order-2--lg module__tools"> <div class="narrow margin-x-auto position-sticky-top font-size-md"> <div class="padding-2 border-radius box-shadow-1--lg"> <div class="tabs" role="tablist"> <nav> <button class="button button--icon-label" id="tab-button-in-this-module" aria-label="Table of Contents" aria-controls="tab-panel-module__tools" aria-selected="true" role="tab"> <span class="icon icon-list" aria-hidden="true"></span> <span class="button__text">Contents</span> </button> <button class="button button--icon-label" id="tab-button-toggle-terms" aria-controls="tab-panel-toggle-terms" aria-selected="false" role="tab"> <span class="icon icon-glossary-highlight"></span> <span class="button__text">Glossary Terms</span> </button> <button class="button button--icon-label" id="tab-button-toggle-ngss" aria-controls="tab-panel-toggle-ngss" aria-selected="false" role="tab"> <span class="icon icon-ngss"></span> <span class="button__text">NGSS</span> </button> </nav> <hr class="divider" /> <div class="tabs__panel shown" id="tab-panel-module__tools" aria-labelledby="tab-button-module__tools" role="tabpanel"> <p class="font-weight-bold margin-bottom-1"> Table of Contents </p> <div class="table-of-contents" id="module-toc"> <ul> <li><a href="/en/library/earth-science/6/identifying-minerals/130#toc_1">Identifying minerals by physical properties</a> </li> <li> <ul> <li><a href="/en/library/earth-science/6/identifying-minerals/130#toc2_1">Color</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/earth-science/6/identifying-minerals/130#toc2_2">Crystal form</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/earth-science/6/identifying-minerals/130#toc2_3">Hardness</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/earth-science/6/identifying-minerals/130#toc2_4">Luster</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/earth-science/6/identifying-minerals/130#toc2_5">Density</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/earth-science/6/identifying-minerals/130#toc2_6">Cleavage and fracture</a> </li> </ul> </li> <li> <ul> <li><a href="/en/library/earth-science/6/identifying-minerals/130#toc2_7">Mineral classification systems</a> </li> </ul> </li> </ul> </div> </div>   <div class="tabs__panel" id="tab-panel-toggle-terms" aria-labelledby="tab-button-toggle-terms" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="termsToggleSwitch" id="terms-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Highlight Glossary Terms </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate glossary term highlighting to easily identify key terms within the module. Once highlighted, you can click on these terms to view their definitions. </em> </p> </div> </div> </div> <div class="tabs__panel" id="tab-panel-toggle-ngss" aria-labelledby="tab-button-toggle-ngss" role="tabpanel"> <div class="reading-toggle"> <div class="reading-toggle__switch"> <div class="form-entry__option__switch"> <label> <input type="checkbox" name="ngssToggleSwitch" id="ngss-toggle-switch" /> <span class="switch__slider"></span> <span class="option__label text-decoration-none font-size-md"> Show NGSS Annotations </span> </label> </div> </div> <div class="reading-toggle__help"> <p> <em> Activate NGSS annotations to easily identify NGSS standards within the module. Once highlighted, you can click on them to view these standards. </em> </p> </div> </div> </div> <div class="reading-annotation-container"></div>  </div> </div> <div class="margin-3"> <script async src="https://pagead2.googlesyndication.com/pagead/js/adsbygoogle.js?client=ca-pub-9561344156007092" crossorigin="anonymous"></script>  <ins class="adsbygoogle" style="display:block" data-ad-client="ca-pub-9561344156007092" data-ad-slot="7634263342" data-ad-format="auto" data-full-width-responsive="true"></ins> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script> </div>   </article> </div> </main> <script id="ngssCommentdata" type="application/json"> [{"ngss_tag_id":null,"type":"p","tag":null,"name":null,"description":null,"comment":"Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students\u2019 own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that 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