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href="#Structure_type"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Structure type</span> </div> </a> <ul id="toc-Structure_type-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header 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</div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Corundum</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 68 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-68" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">68 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Korund" title="Korund – Afrikaans" lang="af" hreflang="af" data-title="Korund" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%83%D9%88%D8%B1%D9%86%D8%AF%D9%85" title="كورندم – Arabic" lang="ar" hreflang="ar" data-title="كورندم" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-an mw-list-item"><a href="https://an.wikipedia.org/wiki/Corind%C3%B3n" title="Corindón – Aragonese" lang="an" hreflang="an" data-title="Corindón" data-language-autonym="Aragonés" data-language-local-name="Aragonese" class="interlanguage-link-target"><span>Aragonés</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Korund" title="Korund – Azerbaijani" lang="az" hreflang="az" data-title="Korund" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%9A%D0%B0%D1%80%D1%83%D0%BD%D0%B4" title="Карунд – Belarusian" lang="be" hreflang="be" data-title="Карунд" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%9A%D0%B0%D1%80%D1%83%D0%BD%D0%B4" title="Карунд – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="Карунд" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%9A%D0%BE%D1%80%D1%83%D0%BD%D0%B4" title="Корунд – Bulgarian" lang="bg" hreflang="bg" data-title="Корунд" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Korund" title="Korund – Bosnian" lang="bs" hreflang="bs" data-title="Korund" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Corind%C3%B3" title="Corindó – Catalan" lang="ca" hreflang="ca" data-title="Corindó" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Korund" title="Korund – Czech" lang="cs" hreflang="cs" data-title="Korund" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Korund" title="Korund – Danish" lang="da" hreflang="da" data-title="Korund" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de badge-Q17437796 badge-featuredarticle mw-list-item" title="featured article badge"><a href="https://de.wikipedia.org/wiki/Korund" title="Korund – German" lang="de" hreflang="de" data-title="Korund" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Korund" title="Korund – Estonian" lang="et" hreflang="et" data-title="Korund" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%9A%CE%BF%CF%81%CE%BF%CF%8D%CE%BD%CE%B4%CE%B9%CE%BF" title="Κορούνδιο – Greek" lang="el" hreflang="el" data-title="Κορούνδιο" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Corind%C3%B3n" title="Corindón – Spanish" lang="es" hreflang="es" data-title="Corindón" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Korundo" title="Korundo – Esperanto" lang="eo" hreflang="eo" data-title="Korundo" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Korindoi" title="Korindoi – Basque" lang="eu" hreflang="eu" data-title="Korindoi" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%DA%A9%D8%B1%D9%86%D8%AF%D9%88%D9%85" title="کرندوم – Persian" lang="fa" hreflang="fa" data-title="کرندوم" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Corindon" title="Corindon – French" lang="fr" hreflang="fr" data-title="Corindon" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-fy mw-list-item"><a href="https://fy.wikipedia.org/wiki/Korund" title="Korund – Western Frisian" lang="fy" hreflang="fy" data-title="Korund" data-language-autonym="Frysk" data-language-local-name="Western Frisian" class="interlanguage-link-target"><span>Frysk</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Corandam" title="Corandam – Irish" lang="ga" hreflang="ga" data-title="Corandam" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Corind%C3%B3n" title="Corindón – Galician" lang="gl" hreflang="gl" data-title="Corindón" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-hak mw-list-item"><a href="https://hak.wikipedia.org/wiki/K%C3%B4ng-ngiu%CC%8Dk" title="Kông-ngiu̍k – Hakka Chinese" lang="hak" hreflang="hak" data-title="Kông-ngiu̍k" data-language-autonym="客家語 / Hak-kâ-ngî" data-language-local-name="Hakka Chinese" class="interlanguage-link-target"><span>客家語 / Hak-kâ-ngî</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EA%B0%95%EC%98%A5" title="강옥 – Korean" lang="ko" hreflang="ko" data-title="강옥" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D4%BF%D5%B8%D6%80%D5%B8%D6%82%D5%B6%D5%A4" title="Կորունդ – Armenian" lang="hy" hreflang="hy" data-title="Կորունդ" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%95%E0%A5%81%E0%A4%B0%E0%A5%81%E0%A4%B5%E0%A4%BF%E0%A4%A8%E0%A5%8D%E0%A4%A6" title="कुरुविन्द – Hindi" lang="hi" hreflang="hi" data-title="कुरुविन्द" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Korund" title="Korund – Croatian" lang="hr" hreflang="hr" data-title="Korund" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-io mw-list-item"><a href="https://io.wikipedia.org/wiki/Korundo" title="Korundo – Ido" lang="io" hreflang="io" data-title="Korundo" data-language-autonym="Ido" data-language-local-name="Ido" class="interlanguage-link-target"><span>Ido</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Korundum" title="Korundum – Indonesian" lang="id" hreflang="id" data-title="Korundum" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-ia mw-list-item"><a href="https://ia.wikipedia.org/wiki/Corundo" title="Corundo – Interlingua" lang="ia" hreflang="ia" data-title="Corundo" data-language-autonym="Interlingua" data-language-local-name="Interlingua" class="interlanguage-link-target"><span>Interlingua</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Corindone" title="Corindone – Italian" lang="it" hreflang="it" data-title="Corindone" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%A7%D7%95%D7%A8%D7%95%D7%A0%D7%93%D7%95%D7%9D" title="קורונדום – Hebrew" lang="he" hreflang="he" data-title="קורונדום" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%99%E1%83%9D%E1%83%A0%E1%83%A3%E1%83%9C%E1%83%93%E1%83%98" title="კორუნდი – Georgian" lang="ka" hreflang="ka" data-title="კორუნდი" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%9A%D0%BE%D1%80%D1%83%D0%BD%D0%B4" title="Корунд – Kazakh" lang="kk" hreflang="kk" data-title="Корунд" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Corundum" title="Corundum – Latin" lang="la" hreflang="la" data-title="Corundum" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Korunds" title="Korunds – Latvian" lang="lv" hreflang="lv" data-title="Korunds" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Korundas" title="Korundas – Lithuanian" lang="lt" hreflang="lt" data-title="Korundas" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Korund" title="Korund – Hungarian" lang="hu" hreflang="hu" data-title="Korund" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mg mw-list-item"><a href="https://mg.wikipedia.org/wiki/K%C3%B4rind%C3%B4na" title="Kôrindôna – Malagasy" lang="mg" hreflang="mg" data-title="Kôrindôna" data-language-autonym="Malagasy" data-language-local-name="Malagasy" class="interlanguage-link-target"><span>Malagasy</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Korund" title="Korund – Dutch" lang="nl" hreflang="nl" data-title="Korund" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%82%B3%E3%83%A9%E3%83%B3%E3%83%80%E3%83%A0" title="コランダム – Japanese" lang="ja" hreflang="ja" data-title="コランダム" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Korund" title="Korund – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Korund" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Korund" title="Korund – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Korund" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Corindon" title="Corindon – Occitan" lang="oc" hreflang="oc" data-title="Corindon" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Korund" title="Korund – Uzbek" lang="uz" hreflang="uz" data-title="Korund" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="Uzbek" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-ps mw-list-item"><a href="https://ps.wikipedia.org/wiki/%DA%A9%D9%88%D8%B1%D9%86%DA%89%D9%85" title="کورنډم – Pashto" lang="ps" hreflang="ps" data-title="کورنډم" data-language-autonym="پښتو" data-language-local-name="Pashto" class="interlanguage-link-target"><span>پښتو</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Korund" title="Korund – Polish" lang="pl" hreflang="pl" data-title="Korund" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Cor%C3%ADndon" title="Coríndon – Portuguese" lang="pt" hreflang="pt" data-title="Coríndon" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Corindon" title="Corindon – Romanian" lang="ro" hreflang="ro" data-title="Corindon" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%9A%D0%BE%D1%80%D1%83%D0%BD%D0%B4" title="Корунд – Russian" lang="ru" hreflang="ru" data-title="Корунд" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sah mw-list-item"><a href="https://sah.wikipedia.org/wiki/%D0%9A%D0%BE%D1%80%D1%83%D0%BD%D0%B4" title="Корунд – Yakut" lang="sah" hreflang="sah" data-title="Корунд" data-language-autonym="Саха тыла" data-language-local-name="Yakut" class="interlanguage-link-target"><span>Саха тыла</span></a></li><li class="interlanguage-link interwiki-si mw-list-item"><a href="https://si.wikipedia.org/wiki/%E0%B6%9A%E0%B7%94%E0%B6%BB%E0%B7%94%E0%B7%80%E0%B7%92%E0%B6%B1%E0%B7%8A%E0%B6%AF" title="කුරුවින්ද – Sinhala" lang="si" hreflang="si" data-title="කුරුවින්ද" data-language-autonym="සිංහල" data-language-local-name="Sinhala" class="interlanguage-link-target"><span>සිංහල</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Corundum" title="Corundum – Simple English" lang="en-simple" hreflang="en-simple" data-title="Corundum" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Korund" title="Korund – Slovak" lang="sk" hreflang="sk" data-title="Korund" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Korund" title="Korund – Slovenian" lang="sl" hreflang="sl" data-title="Korund" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" 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</div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Oxide mineral</div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/Carborundum" class="mw-redirect" title="Carborundum">Carborundum</a> or <a href="/wiki/Conundrum_(disambiguation)" class="mw-redirect mw-disambig" title="Conundrum (disambiguation)">Conundrum</a>.</div> <p class="mw-empty-elt"> </p> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox"><tbody><tr><th colspan="2" class="infobox-above" style="color:black; background-color: #8BAFDA">Corundum</th></tr><tr><td colspan="2" class="infobox-image"><span typeof="mw:File"><a href="/wiki/File:Several_corundum_crystals.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Several_corundum_crystals.jpg/260px-Several_corundum_crystals.jpg" decoding="async" width="260" height="206" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Several_corundum_crystals.jpg/390px-Several_corundum_crystals.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/9/9a/Several_corundum_crystals.jpg/520px-Several_corundum_crystals.jpg 2x" data-file-width="1677" data-file-height="1331" /></a></span></td></tr><tr><th colspan="2" class="infobox-header" style="color:black; background-color: #8BAFDA">General</th></tr><tr><th scope="row" class="infobox-label">Category</th><td class="infobox-data"><a href="/wiki/Oxide_mineral" title="Oxide mineral">Oxide mineral</a> – Hematite group</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Chemical_formula" title="Chemical formula">Formula</a><br /><style data-mw-deduplicate="TemplateStyles:r886047488">.mw-parser-output .nobold{font-weight:normal}</style><span class="nobold">(repeating unit)</span></th><td class="infobox-data">Al<sub>2</sub>O<sub>3</sub></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/List_of_mineral_symbols" title="List of mineral symbols">IMA symbol</a></th><td class="infobox-data">Crn<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Nickel%E2%80%93Strunz_classification" title="Nickel–Strunz classification">Strunz classification</a></th><td class="infobox-data">4.CB.05</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Dana_Classification_System" class="mw-redirect" title="Dana Classification System">Dana classification</a></th><td class="infobox-data">4.3.1.1</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Crystal_system" title="Crystal system">Crystal system</a></th><td class="infobox-data"><a href="/wiki/Trigonal" class="mw-redirect" title="Trigonal">Trigonal</a></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Crystal_class" class="mw-redirect" title="Crystal class">Crystal class</a></th><td class="infobox-data">Hexagonal scalenohedral (<span style="text-decoration:overline;">3</span>m)<br /><a href="/wiki/H-M_symbol" class="mw-redirect" title="H-M symbol">H-M symbol</a>: (<span style="text-decoration:overline;">3</span> 2/m)</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Space_group" title="Space group">Space group</a></th><td class="infobox-data"><span class="texhtml mvar" style="font-style:italic;">R</span><span style="text-decoration:overline;">3</span><span class="texhtml mvar" style="font-style:italic;">c</span> (No. 167)</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Crystal_structure#Unit_cell" title="Crystal structure">Unit cell</a></th><td class="infobox-data"><span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">a</span> = 4.75 Å</span>, <span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">c</span> = 12.982 Å</span>; <span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">Z</span> = 6</span></td></tr><tr><th colspan="2" class="infobox-header" style="color:black; background-color: #8BAFDA">Identification</th></tr><tr><th scope="row" class="infobox-label">Color</th><td class="infobox-data">Colorless, gray, golden-brown, brown; purple, pink to red, orange, yellow, green, blue, violet; may be color zoned, asteriated mainly grey and brown</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Crystal_habit" title="Crystal habit">Crystal habit</a></th><td class="infobox-data">Steep bipyramidal, tabular, prismatic, rhombohedral crystals, massive or granular</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Crystal_twinning" title="Crystal twinning">Twinning</a></th><td class="infobox-data">Polysynthetic twinning common</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Cleavage_(crystal)" title="Cleavage (crystal)">Cleavage</a></th><td class="infobox-data">None – parting in 3 directions</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Fracture_(mineralogy)" title="Fracture (mineralogy)">Fracture</a></th><td class="infobox-data">Conchoidal to uneven</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Tenacity_(mineralogy)" title="Tenacity (mineralogy)">Tenacity</a></th><td class="infobox-data">Brittle</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Mohs_scale_of_mineral_hardness" class="mw-redirect" title="Mohs scale of mineral hardness">Mohs scale</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886047488"><span class="nobold">hardness</span></th><td class="infobox-data">9 (defining mineral)<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Lustre_(mineralogy)" title="Lustre (mineralogy)">Luster</a></th><td class="infobox-data">Adamantine to vitreous</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Streak_(mineralogy)" title="Streak (mineralogy)">Streak</a></th><td class="infobox-data">Colorless</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Transparency_and_translucency" title="Transparency and translucency">Diaphaneity</a></th><td class="infobox-data">Transparent, <a href="/wiki/Translucent" class="mw-redirect" title="Translucent">translucent</a> to <a href="/wiki/Opacity_(optics)" class="mw-redirect" title="Opacity (optics)">opaque</a></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Specific_gravity" class="mw-redirect" title="Specific gravity">Specific gravity</a></th><td class="infobox-data">3.95–4.10</td></tr><tr><th scope="row" class="infobox-label">Optical properties</th><td class="infobox-data">Uniaxial (−)</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Refractive_index" title="Refractive index">Refractive index</a></th><td class="infobox-data"><span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">n</span><sub><span class="texhtml">ω</span></sub> = 1.767–1.772</span> <br /><span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">n</span><sub><span class="texhtml">ε</span></sub> = 1.759–1.763</span></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Pleochroism" title="Pleochroism">Pleochroism</a></th><td class="infobox-data">None</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Melting_point" title="Melting point">Melting point</a></th><td class="infobox-data">2,044 °C (3,711 °F)</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Fusibility" title="Fusibility">Fusibility</a></th><td class="infobox-data">Infusible</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Solubility" title="Solubility">Solubility</a></th><td class="infobox-data">Insoluble</td></tr><tr><th scope="row" class="infobox-label">Alters to</th><td class="infobox-data">May alter to mica on surfaces causing a decrease in hardness</td></tr><tr><th scope="row" class="infobox-label">Other characteristics</th><td class="infobox-data">May fluoresce or phosphoresce under UV light</td></tr><tr><th scope="row" class="infobox-label">References</th><td class="infobox-data"><sup id="cite_ref-Handbook_3-0" class="reference"><a href="#cite_note-Handbook-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Mindat_4-0" class="reference"><a href="#cite_note-Mindat-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Webmin_5-0" class="reference"><a href="#cite_note-Webmin-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Hurlbut_6-0" class="reference"><a href="#cite_note-Hurlbut-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup></td></tr><tr><th colspan="2" class="infobox-header" style="color:black; background-color: #8BAFDA">Major varieties</th></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Sapphire" title="Sapphire">Sapphire</a></th><td class="infobox-data">Any color except red</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Ruby" title="Ruby">Ruby</a></th><td class="infobox-data">Red</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Emery_(mineral)" class="mw-redirect" title="Emery (mineral)">Emery</a></th><td class="infobox-data">Black granular corundum intimately mixed with <a href="/wiki/Magnetite" title="Magnetite">magnetite</a>, <a href="/wiki/Hematite" title="Hematite">hematite</a>, or <a href="/wiki/Hercynite" title="Hercynite">hercynite</a></td></tr></tbody></table> <p><b>Corundum</b> is a <a href="/wiki/Crystal" title="Crystal">crystalline</a> form of <a href="/wiki/Aluminium_oxide" title="Aluminium oxide">aluminium oxide</a> (<style data-mw-deduplicate="TemplateStyles:r1123817410">.mw-parser-output .template-chem2-su{display:inline-block;font-size:80%;line-height:1;vertical-align:-0.35em}.mw-parser-output .template-chem2-su>span{display:block;text-align:left}.mw-parser-output sub.template-chem2-sub{font-size:80%;vertical-align:-0.35em}.mw-parser-output sup.template-chem2-sup{font-size:80%;vertical-align:0.65em}</style><span class="chemf nowrap">Al<sub class="template-chem2-sub">2</sub>O<sub class="template-chem2-sub">3</sub></span>) typically containing traces of <a href="/wiki/Iron" title="Iron">iron</a>, <a href="/wiki/Titanium" title="Titanium">titanium</a>, <a href="/wiki/Vanadium" title="Vanadium">vanadium</a>, and <a href="/wiki/Chromium" title="Chromium">chromium</a>.<sup id="cite_ref-Handbook_3-1" class="reference"><a href="#cite_note-Handbook-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Mindat_4-1" class="reference"><a href="#cite_note-Mindat-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> It is a <a href="/wiki/Rock_(geology)" title="Rock (geology)">rock</a>-forming <a href="/wiki/Mineral" title="Mineral">mineral</a>. It is a naturally <a href="/wiki/Transparency_and_translucency" title="Transparency and translucency">transparent</a> material, but can have different colors depending on the presence of <a href="/wiki/Transition_metal" title="Transition metal">transition metal</a> impurities in its crystalline structure.<sup id="cite_ref-:0_7-0" class="reference"><a href="#cite_note-:0-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> Corundum has two primary gem varieties: <a href="/wiki/Ruby" title="Ruby">ruby</a> and <a href="/wiki/Sapphire" title="Sapphire">sapphire</a>. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present.<sup id="cite_ref-:0_7-1" class="reference"><a href="#cite_note-:0-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> A rare type of sapphire, <a href="/wiki/Sapphire#Padparadscha" title="Sapphire">padparadscha</a> sapphire, is pink-orange. </p><p>The name "corundum" is derived from the <a href="/wiki/Tamil_language" title="Tamil language">Tamil</a>-<a href="/wiki/Dravidian_languages" title="Dravidian languages">Dravidian</a> word <i>kurundam</i> (ruby-sapphire) (appearing in <a href="/wiki/Sanskrit" title="Sanskrit">Sanskrit</a> as <i>kuruvinda</i>).<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> </p><p>Because of corundum's hardness (pure corundum is defined to have 9.0 on the <a href="/wiki/Mohs_scale" title="Mohs scale">Mohs scale</a>), it can scratch almost all other minerals. It is commonly used as an <a href="/wiki/Abrasive" title="Abrasive">abrasive</a> on <a href="/wiki/Sandpaper" title="Sandpaper">sandpaper</a> and on large tools used in machining metals, plastics, and wood. <a href="/wiki/Emery_(rock)" title="Emery (rock)">Emery</a>, a variety of corundum with no value as a gemstone, is commonly used as an abrasive. It is a black granular form of corundum, in which the mineral is intimately mixed with <a href="/wiki/Magnetite" title="Magnetite">magnetite</a>, <a href="/wiki/Hematite" title="Hematite">hematite</a>, or <a href="/wiki/Hercynite" title="Hercynite">hercynite</a>.<sup id="cite_ref-Hurlbut_6-1" class="reference"><a href="#cite_note-Hurlbut-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>In addition to its hardness, corundum has a density of 4.02 g/cm<sup>3</sup> (251 lb/cu ft), which is unusually high for a transparent mineral composed of the low-<a href="/wiki/Atomic_mass" title="Atomic mass">atomic mass</a> elements <a href="/wiki/Aluminium" title="Aluminium">aluminium</a> and <a href="/wiki/Oxygen" title="Oxygen">oxygen</a>.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Geology_and_occurrence">Geology and occurrence</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Corundum&action=edit&section=1" title="Edit section: Geology and occurrence"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Corindon_azulEZ.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Corindon_azulEZ.jpg/180px-Corindon_azulEZ.jpg" decoding="async" width="180" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Corindon_azulEZ.jpg/270px-Corindon_azulEZ.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Corindon_azulEZ.jpg/360px-Corindon_azulEZ.jpg 2x" data-file-width="420" data-file-height="350" /></a><figcaption>Corundum from <a href="/wiki/Brazil" title="Brazil">Brazil</a>, size about 2 cm × 3 cm (0.8 in × 1 in)</figcaption></figure> <p>Corundum occurs as a mineral in mica <a href="/wiki/Schist" title="Schist">schist</a>, <a href="/wiki/Gneiss" title="Gneiss">gneiss</a>, and some <a href="/wiki/Marble" title="Marble">marbles</a> in <a href="/wiki/Metamorphic" class="mw-redirect" title="Metamorphic">metamorphic</a> <a href="/wiki/Terrane" title="Terrane">terranes</a>. It also occurs in low-silica <a href="/wiki/Igneous" class="mw-redirect" title="Igneous">igneous</a> <a href="/wiki/Syenite" title="Syenite">syenite</a> and <a href="/wiki/Nepheline_syenite" title="Nepheline syenite">nepheline syenite</a> <a href="/wiki/Intrusive_rock" title="Intrusive rock">intrusives</a>. Other occurrences are as masses adjacent to <a href="/wiki/Ultramafic" class="mw-redirect" title="Ultramafic">ultramafic</a> intrusives, associated with <a href="/wiki/Lamprophyre" title="Lamprophyre">lamprophyre</a> <a href="/wiki/Dike_(geology)" title="Dike (geology)">dikes</a> and as large crystals in <a href="/wiki/Pegmatite" title="Pegmatite">pegmatites</a>.<sup id="cite_ref-Hurlbut_6-2" class="reference"><a href="#cite_note-Hurlbut-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> It commonly occurs as a <a href="/wiki/Detrital" class="mw-redirect" title="Detrital">detrital</a> mineral in stream and beach sands because of its hardness and resistance to weathering.<sup id="cite_ref-Hurlbut_6-3" class="reference"><a href="#cite_note-Hurlbut-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> The largest documented single crystal of corundum measured about 65 cm × 40 cm × 40 cm (26 in × 16 in × 16 in), and weighed 152 kg (335 lb).<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> The record has since been surpassed by certain synthetic <a href="/wiki/Boule_(crystal)" title="Boule (crystal)">boules</a>.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p><p>Corundum for <a href="/wiki/Abrasive" title="Abrasive">abrasives</a> is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India. Historically it was mined from deposits associated with <a href="/wiki/Dunite" title="Dunite">dunites</a> in <a href="/wiki/North_Carolina" title="North Carolina">North Carolina</a>, US, and from a nepheline syenite in <a href="/wiki/Craigmont,_Ontario" title="Craigmont, Ontario">Craigmont, Ontario</a>.<sup id="cite_ref-Hurlbut_6-4" class="reference"><a href="#cite_note-Hurlbut-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Emery_(mineral)" class="mw-redirect" title="Emery (mineral)">Emery</a>-grade corundum is found on the <a href="/wiki/List_of_islands_of_Greece" title="List of islands of Greece">Greek island</a> of <a href="/wiki/Naxos" title="Naxos">Naxos</a> and near <a href="/wiki/Peekskill,_New_York" title="Peekskill, New York">Peekskill, New York</a>, US. Abrasive corundum is synthetically manufactured from <a href="/wiki/Bauxite" title="Bauxite">bauxite</a>.<sup id="cite_ref-Hurlbut_6-5" class="reference"><a href="#cite_note-Hurlbut-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p><p>Four corundum axes dating to 2500 BC from the <a href="/wiki/Liangzhu_culture" title="Liangzhu culture">Liangzhu culture</a> and Sanxingcun culture (the latter of which is located in <a href="/wiki/Jintan_District" class="mw-redirect" title="Jintan District">Jintan District</a>) have been discovered in China.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Synthetic_corundum">Synthetic corundum</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Corundum&action=edit&section=2" title="Edit section: Synthetic corundum"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>In 1837, <a href="/wiki/Marc_Antoine_Auguste_Gaudin" title="Marc Antoine Auguste Gaudin">Marc Antoine Gaudin</a> made the first synthetic rubies by reacting <a href="/wiki/Alumina" class="mw-redirect" title="Alumina">alumina</a> at a high temperature with a small amount of <a href="/wiki/Chromium" title="Chromium">chromium</a> as a <a href="/wiki/Colourant" title="Colourant">colourant</a>.<sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup></li> <li>In 1847, <a href="/wiki/Jacques-Joseph_Ebelmen" title="Jacques-Joseph Ebelmen">J. J. Ebelmen</a> made white <a href="/wiki/Sapphire#Synthetic_sapphire" title="Sapphire">synthetic sapphires</a> by reacting <a href="/wiki/Aluminium_oxide" title="Aluminium oxide">alumina</a> in <a href="/wiki/Boric_acid" title="Boric acid">boric acid</a>.</li> <li>In 1877, Frenic and Freil made crystal corundum from which small stones could be cut. Frimy and <a href="/wiki/Auguste_Victor_Louis_Verneuil" title="Auguste Victor Louis Verneuil">Auguste Verneuil</a> manufactured artificial ruby by fusing <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1123817410"><span class="chemf nowrap"><a href="/wiki/Barium_fluoride" title="Barium fluoride">BaF<sub class="template-chem2-sub">2</sub></a></span> and <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1123817410"><span class="chemf nowrap"><a href="/wiki/Aluminium_oxide" title="Aluminium oxide">Al<sub class="template-chem2-sub">2</sub>O<sub class="template-chem2-sub">3</sub></a></span> with a little chromium at temperatures above 2,000 °C (3,630 °F).</li> <li>In 1903, <a href="/wiki/Auguste_Victor_Louis_Verneuil" title="Auguste Victor Louis Verneuil">Verneuil</a> announced that he could produce synthetic rubies on a commercial scale using this <a href="/wiki/Flame_fusion" class="mw-redirect" title="Flame fusion">flame fusion</a> process.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup></li></ul> <p>The <a href="/wiki/Verneuil_process" class="mw-redirect" title="Verneuil process">Verneuil process</a> allows the production of flawless single-crystal <a href="/wiki/Sapphire" title="Sapphire">sapphire</a> and <a href="/wiki/Ruby" title="Ruby">ruby</a> gems of much larger size than normally found in nature. It is also possible to grow gem-quality synthetic corundum by flux-growth and <a href="/wiki/Hydrothermal_synthesis" title="Hydrothermal synthesis">hydrothermal synthesis</a>. Because of the simplicity of the methods involved in corundum synthesis, large quantities of these crystals have become available on the market at a fraction of the cost of natural stones.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p><p>Synthetic corundum has a lower environmental impact than natural corundum by avoiding destructive mining and conserving resources.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> However, its production is energy-intensive, contributing to <a href="/wiki/Carbon" title="Carbon">carbon</a> emissions if fossil fuels are used, and involves chemicals that can pose risks.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p><p>Apart from ornamental uses, synthetic corundum is also used to produce mechanical parts (tubes, rods, bearings, and other machined parts), scratch-resistant optics, scratch-resistant <a href="/wiki/Watch#Overview" title="Watch">watch</a> crystals, instrument windows for satellites and spacecraft (because of its transparency in the ultraviolet to infrared range), and <a href="/wiki/Laser" title="Laser">laser</a> components. For example, the <a href="/wiki/KAGRA" title="KAGRA">KAGRA</a> gravitational wave detector's main mirrors are 23 kg (50 lb) sapphires,<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> and <a href="/wiki/Advanced_LIGO" class="mw-redirect" title="Advanced LIGO">Advanced LIGO</a> considered 40 kg (88 lb) sapphire mirrors.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> Corundum has also found use in the development of ceramic armour thanks to its high hardiness.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Structure_and_physical_properties">Structure and physical properties</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Corundum&action=edit&section=3" title="Edit section: Structure and physical properties"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-left" typeof="mw:File/Thumb"><a href="/wiki/File:Corundum.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Corundum.png/250px-Corundum.png" decoding="async" width="250" height="215" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Corundum.png/375px-Corundum.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Corundum.png/500px-Corundum.png 2x" data-file-width="800" data-file-height="688" /></a><figcaption>Crystal structure of corundum</figcaption></figure> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Corundum-pV.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/49/Corundum-pV.svg/250px-Corundum-pV.svg.png" decoding="async" width="250" height="188" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/49/Corundum-pV.svg/375px-Corundum-pV.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/49/Corundum-pV.svg/500px-Corundum-pV.svg.png 2x" data-file-width="720" data-file-height="540" /></a><figcaption>Molar volume vs. pressure at room temperature</figcaption></figure> <p>Corundum crystallizes with trigonal symmetry in the space group <a href="/wiki/Hexagonal_crystal_family#Crystal_classes" title="Hexagonal crystal family"><span class="texhtml mvar" style="font-style:italic;">R</span><span style="text-decoration:overline;">3</span><span class="texhtml mvar" style="font-style:italic;">c</span></a> and has the lattice parameters <span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">a</span> = 4.75 Å</span> and <span class="nowrap"><span class="texhtml mvar" style="font-style:italic;">c</span> = 12.982 Å</span> at standard conditions. The unit cell contains six formula units.<sup id="cite_ref-Mindat_4-2" class="reference"><a href="#cite_note-Mindat-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>The toughness of corundum is sensitive to surface roughness<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> and crystallographic orientation.<sup id="cite_ref-Fracture_of_Sapphire_27-0" class="reference"><a href="#cite_note-Fracture_of_Sapphire-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> It may be 6–7 MPa·m<sup>1/2</sup> for synthetic crystals,<sup id="cite_ref-Fracture_of_Sapphire_27-1" class="reference"><a href="#cite_note-Fracture_of_Sapphire-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> and around 4 MPa·m<sup>1/2</sup> for natural.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </p><p>In the lattice of corundum, the oxygen atoms form a slightly distorted <a href="/wiki/Hexagonal_close_packing" class="mw-redirect" title="Hexagonal close packing">hexagonal close packing</a>, in which two-thirds of the octahedral sites between the oxygen ions are occupied by aluminium ions.<sup id="cite_ref-nesse_29-0" class="reference"><a href="#cite_note-nesse-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> The absence of aluminium ions from one of the three sites breaks the symmetry of the hexagonal close packing, reducing the space group symmetry to <span class="texhtml mvar" style="font-style:italic;">R</span><span style="text-decoration:overline;">3</span><span class="texhtml mvar" style="font-style:italic;">c</span> and the crystal class to trigonal.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> The structure of corundum is sometimes described as a pseudohexagonal structure.<sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p><p>The Young's modulus of corundum (sapphire) has been reported by many different sources with values varying between 300 and 500 GPa, but a commonly cited value used for calculations is 345 GPa.<sup id="cite_ref-:1_32-0" class="reference"><a href="#cite_note-:1-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> The Young's modulus is temperature dependent, and has been reported in the [0001] direction as 435 GPa at 323 K and 386 GPa at 1,273 K.<sup id="cite_ref-:1_32-1" class="reference"><a href="#cite_note-:1-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> The shear modulus of corundum is 145 GPa,<sup id="cite_ref-:2_33-0" class="reference"><a href="#cite_note-:2-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> and the bulk modulus is 240 GPa.<sup id="cite_ref-:2_33-1" class="reference"><a href="#cite_note-:2-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> </p><p>Single crystal corundum fibers have potential applications in high temperature composites, and the Young's modulus is highly dependent on the crystallographic orientation along the fiber axis. The fiber exhibits a max modulus of 461 GPa when the crystallographic c-axis [0001] is aligned with the fiber axis, and minimum moduli ~373 GPa when a direction 45° away from the c-axis is aligned with the fiber axis.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> </p><p>The hardness of corundum measured by indentation at low loads of 1-2 N has been reported as 22-23 GPa<sup id="cite_ref-:3_35-0" class="reference"><a href="#cite_note-:3-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> in major crystallographic planes: (0001) (basal plane), (10<span style="text-decoration:overline;">1</span>0) (rhombohedral plane), (11<span style="text-decoration:overline;">2</span>0) (prismatic plane), and (10<span style="text-decoration:overline;">1</span>2). The hardness can drop significantly under high indentation loads. The drop with respect to load varies with the crystallographic plane due to the difference in crack resistance and propagation between directions. One extreme case is seen in the (0001) plane, where the hardness under high load (~1 kN) is nearly half the value under low load (1-2 N).<sup id="cite_ref-:3_35-1" class="reference"><a href="#cite_note-:3-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p><p>Polycrystalline corundum formed through sintering and treated with a hot isostatic press process can achieve grain sizes in the range of 0.55-0.7 μm, and has been measured to have four-point bending strength between 600 and 700 MPa and three-point bending strength between 750 and 900 MPa.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Structure_type">Structure type</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Corundum&action=edit&section=4" title="Edit section: Structure type"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Corundum_(structure)" title="Corundum (structure)">Corundum (structure)</a></div> <p>Because of its prevalence, corundum has also become the name of a major structure type (<i>corundum type</i>) found in various <a href="/wiki/Binary_compound" class="mw-redirect" title="Binary compound">binary</a> and <a href="/wiki/Ternary_compound" title="Ternary compound">ternary compounds</a>.<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Corundum&action=edit&section=5" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output .side-box-image{padding:2px 0 2px 0.9em;text-align:center}.mw-parser-output .side-box-imageright{padding:2px 0.9em 2px 0;text-align:center}@media(min-width:500px){.mw-parser-output .side-box-flex{display:flex;align-items:center}.mw-parser-output .side-box-text{flex:1;min-width:0}}@media(min-width:720px){.mw-parser-output .side-box{width:238px}.mw-parser-output .side-box-right{clear:right;float:right;margin-left:1em}.mw-parser-output .side-box-left{margin-right:1em}}</style><style data-mw-deduplicate="TemplateStyles:r1237033735">@media print{body.ns-0 .mw-parser-output .sistersitebox{display:none!important}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .sistersitebox img[src*="Wiktionary-logo-en-v2.svg"]{background-color:white}}</style><div class="side-box side-box-right plainlinks sistersitebox"><style data-mw-deduplicate="TemplateStyles:r1126788409">.mw-parser-output .plainlist ol,.mw-parser-output .plainlist ul{line-height:inherit;list-style:none;margin:0;padding:0}.mw-parser-output .plainlist ol li,.mw-parser-output .plainlist ul li{margin-bottom:0}</style> <div class="side-box-flex"> <div class="side-box-image"><span class="noviewer" typeof="mw:File"><span><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" decoding="async" width="30" height="40" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span></div> <div class="side-box-text plainlist">Wikimedia Commons has media related to <span style="font-weight: bold; font-style: italic;"><a href="https://commons.wikimedia.org/wiki/Category:Corundum" class="extiw" title="commons:Category:Corundum">Corundum</a></span>.</div></div> </div> <ul><li><a href="/wiki/Aluminium_oxynitride" title="Aluminium oxynitride">Aluminium oxynitride</a></li> <li><a href="/wiki/Gemstone" title="Gemstone">Gemstone</a></li> <li><a href="/wiki/Spinel" title="Spinel">Spinel</a> – natural and synthetic mineral often mistaken for corundum</li></ul> <div style="clear:left;" class=""></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Corundum&action=edit&section=6" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 25em;"> <ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFWarr2021" class="citation journal cs1">Warr, L.N. (2021). <a rel="nofollow" class="external text" href="https://doi.org/10.1180%2Fmgm.2021.43">"IMA–CNMNC approved mineral symbols"</a>. <i>Mineralogical Magazine</i>. <b>85</b> (3): 291–320. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2021MinM...85..291W">2021MinM...85..291W</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1180%2Fmgm.2021.43">10.1180/mgm.2021.43</a></span>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:235729616">235729616</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Mineralogical+Magazine&rft.atitle=IMA%E2%80%93CNMNC+approved+mineral+symbols&rft.volume=85&rft.issue=3&rft.pages=291-320&rft.date=2021&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A235729616%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1180%2Fmgm.2021.43&rft_id=info%3Abibcode%2F2021MinM...85..291W&rft.aulast=Warr&rft.aufirst=L.N.&rft_id=https%3A%2F%2Fdoi.org%2F10.1180%252Fmgm.2021.43&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACorundum" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.minsocam.org/msa/collectors_corner/article/mohs.htm">"Mohs' scale of hardness"</a>. <i>Collector's corner</i>. Mineralogical Society of America<span class="reference-accessdate">. Retrieved <span class="nowrap">10 January</span> 2014</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Collector%27s+corner&rft.atitle=Mohs%27+scale+of+hardness&rft_id=http%3A%2F%2Fwww.minsocam.org%2Fmsa%2Fcollectors_corner%2Farticle%2Fmohs.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACorundum" class="Z3988"></span></span> </li> <li id="cite_note-Handbook-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-Handbook_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Handbook_3-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFAnthony,_John_W.Bideaux,_Richard_A.Bladh,_Kenneth_W.Nichols,_Monte_C.1997" class="citation book cs1 cs1-prop-long-vol">Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (1997). 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Boca Raton: CRC Press. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1201%2F9780429283260">10.1201/9780429283260</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-429-28326-0" title="Special:BookSources/978-0-429-28326-0"><bdi>978-0-429-28326-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Physical+Properties+of+Diamond+and+Sapphire&rft.place=Boca+Raton&rft.pub=CRC+Press&rft.date=2019-05-03&rft_id=info%3Adoi%2F10.1201%2F9780429283260&rft.isbn=978-0-429-28326-0&rft.aulast=Ramdas&rft.aufirst=Roshan+L.+Aggarwal%2C+Anant+K.&rft_id=https%3A%2F%2Fwww.taylorfrancis.com%2Fbooks%2Fmono%2F10.1201%2F9780429283260%2Fphysical-properties-diamond-sapphire-roshan-aggarwal-anant-ramdas&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACorundum" class="Z3988"></span><span class="cs1-maint citation-comment"><code class="cs1-code">{{<a href="/wiki/Template:Cite_book" title="Template:Cite book">cite book</a>}}</code>: CS1 maint: multiple names: authors list (<a href="/wiki/Category:CS1_maint:_multiple_names:_authors_list" title="Category:CS1 maint: multiple names: authors list">link</a>)</span></span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFWadleyLuGoldman1995" class="citation journal cs1">Wadley, Haydn N. 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(1 October 2009). <a rel="nofollow" class="external text" href="https://doi.org/10.3103/S1062873809100177">"Sapphire hardness in different crystallographic directions"</a>. <i>Bulletin of the Russian Academy of Sciences: Physics</i>. <b>73</b> (10): 1380–1382. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.3103%2FS1062873809100177">10.3103/S1062873809100177</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1934-9432">1934-9432</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Bulletin+of+the+Russian+Academy+of+Sciences%3A+Physics&rft.atitle=Sapphire+hardness+in+different+crystallographic+directions&rft.volume=73&rft.issue=10&rft.pages=1380-1382&rft.date=2009-10-01&rft_id=info%3Adoi%2F10.3103%2FS1062873809100177&rft.issn=1934-9432&rft.aulast=Sinani&rft.aufirst=A.+B.&rft.au=Dynkin%2C+N.+K.&rft.au=Lytvinov%2C+L.+A.&rft.au=Konevsky%2C+P.+V.&rft.au=Andreev%2C+E.+P.&rft_id=https%3A%2F%2Fdoi.org%2F10.3103%2FS1062873809100177&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACorundum" class="Z3988"></span></span> </li> <li id="cite_note-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-36">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFKrellBlankMaHutzler2003" class="citation journal cs1">Krell, Andreas; Blank, Paul; Ma, Hongwei; Hutzler, Thomas; van Bruggen, Michel P. B.; Apetz, Rolf (2003). <a rel="nofollow" class="external text" href="https://ceramics.onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.2003.tb03270.x">"Transparent Sintered Corundum with High Hardness and Strength"</a>. <i>Journal of the American Ceramic Society</i>. <b>86</b> (1): 12–18. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fj.1151-2916.2003.tb03270.x">10.1111/j.1151-2916.2003.tb03270.x</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0002-7820">0002-7820</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+the+American+Ceramic+Society&rft.atitle=Transparent+Sintered+Corundum+with+High+Hardness+and+Strength&rft.volume=86&rft.issue=1&rft.pages=12-18&rft.date=2003&rft_id=info%3Adoi%2F10.1111%2Fj.1151-2916.2003.tb03270.x&rft.issn=0002-7820&rft.aulast=Krell&rft.aufirst=Andreas&rft.au=Blank%2C+Paul&rft.au=Ma%2C+Hongwei&rft.au=Hutzler%2C+Thomas&rft.au=van+Bruggen%2C+Michel+P.+B.&rft.au=Apetz%2C+Rolf&rft_id=https%3A%2F%2Fceramics.onlinelibrary.wiley.com%2Fdoi%2F10.1111%2Fj.1151-2916.2003.tb03270.x&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACorundum" class="Z3988"></span></span> </li> <li id="cite_note-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-37">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMullerRoy1974" class="citation book cs1">Muller, Olaf; Roy, Rustum (1974). <a rel="nofollow" class="external text" href="https://www.worldcat.org/oclc/1056558"><i>The major ternary structural families</i></a>. New York: Springer-Verlag. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-387-06430-3" title="Special:BookSources/0-387-06430-3"><bdi>0-387-06430-3</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/1056558">1056558</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+major+ternary+structural+families&rft.place=New+York&rft.pub=Springer-Verlag&rft.date=1974&rft_id=info%3Aoclcnum%2F1056558&rft.isbn=0-387-06430-3&rft.aulast=Muller&rft.aufirst=Olaf&rft.au=Roy%2C+Rustum&rft_id=https%3A%2F%2Fwww.worldcat.org%2Foclc%2F1056558&rfr_id=info%3Asid%2Fen.wikipedia.org%3ACorundum" class="Z3988"></span></span> </li> </ol></div> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output 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