{"id":17868,"date":"2026-04-19T11:35:16","date_gmt":"2026-04-19T06:05:16","guid":{"rendered":"https:\/\/aluminiummagazine.com\/mag\/?p=17868"},"modified":"2026-04-19T11:35:17","modified_gmt":"2026-04-19T06:05:17","slug":"aluminium-silicate-properties-ceramic-guide","status":"publish","type":"post","link":"https:\/\/aluminiummagazine.com\/mag\/aluminium\/compounds\/aluminium-silicate-properties-ceramic-guide.html","title":{"rendered":"Aluminium Silicate (Al\u2082SiO\u2085): The Complete Guide"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Aluminum silicate represents a family of naturally occurring minerals \u2013 andalusite, kyanite, and sillimanite \u2013 all sharing the same chemical formula but differing in crystal structure due to formation under different pressures and temperatures. Industrially, it is valued for its extreme refractoriness (heat resistance) and is used in spark plugs, kiln linings, and catalyst supports.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">1. <strong>Basic Identification<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Chemical Formula:<\/strong> Al\u2082SiO\u2085 (also written as Al\u2082O\u2083\u00b7SiO\u2082)<\/li>\n\n\n\n<li><strong>Alternative Names:<\/strong> Aluminium silicate; mineral names: andalusite, kyanite, sillimanite; heated product: mullite<\/li>\n\n\n\n<li><strong>Molecular Weight:<\/strong> 162.05 g\/mol<\/li>\n\n\n\n<li><strong>CAS Number:<\/strong> 12141-46-7<\/li>\n\n\n\n<li><strong>Appearance:<\/strong> Raw minerals range from blue (kyanite) to brown\/pink\/gray; processed form is white or off\u2011white granular powder<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">2. <strong>Physical Properties<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-center\" data-align=\"center\">Property<\/th><th class=\"has-text-align-center\" data-align=\"center\">Aluminum Silicate (Sillimanite phase \u2013 typical)<\/th><\/tr><\/thead><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Melting Point<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Transitions to mullite ~1450\u20111550\u202f\u00b0C; fully melts &gt;1850\u202f\u00b0C<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Boiling Point<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Decomposes before boiling<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Density<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">3.12 \u2013 3.24 g\/cm\u00b3<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Hardness (Mohs)<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">6.5 \u2013 7.5 (kyanite is anisotropic: 4.5\u20117 depending on direction)<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Solubility<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Insoluble in water, oils, and most industrial solvents<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">The material is inert, non\u2011hygroscopic, and feels like heavy crushed glass or sand.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">3. <strong>Chemical Behavior &amp; Synthesis<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">3.1 Thermal Transformation \u2013 Mullitization<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">When heated above ~1450\u202f\u00b0C, the natural polymorphs convert irreversibly to <strong>mullite<\/strong> (3Al\u2082O\u2083\u00b72SiO\u2082) plus free silica:<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>3 Al\u2082SiO\u2085 \u2192 Al\u2086Si\u2082O\u2081\u2083 + SiO\u2082<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Mullite is one of the most thermally and mechanically stable ceramics known, maintaining rigidity at extreme temperatures.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">3.2 Synthesis<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Most aluminum silicate is mined directly from open\u2011pit quarries. For high\u2011purity applications, synthetic Al\u2082SiO\u2085 is produced by firing finely milled alumina and silica together at &gt;1600\u202f\u00b0C.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">4. <strong>Industrial Applications<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">4.1 High\u2011Temperature Refractories<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Crushed aluminum silicate is used to make bricks that line steel blast furnaces, glass\u2011melting kilns, and incinerators. Unlike ordinary concrete, these bricks glow red but remain rigid under extreme heat.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">4.2 Spark Plug Insulators<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The white ceramic jacket around a spark plug\u2019s metal core is predominantly aluminum silicate. It provides electrical insulation while withstanding thousands of explosive detonations inside the engine.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">4.3 Catalyst Support Beds<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">In petrochemical refineries, porous aluminum silicate pellets or honeycombs serve as inert skeletons that hold reactive catalysts. They allow gas flow while keeping the active chemistry in place.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">5. <strong>Safety &amp; Hazard Management<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>General Safety:<\/strong> Aluminum silicate is naturally occurring and non\u2011toxic, but fine dust can cause mechanical lung damage.<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-center\" data-align=\"center\">Route of Exposure<\/th><th>Effect<\/th><\/tr><\/thead><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Inhalation<\/strong><\/td><td>Primary hazard. Chronic exposure to fine crystalline dust may cause pneumoconiosis (silicosis).<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Skin Contact<\/strong><\/td><td>No chemical hazard; may act as an abrasive.<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Eye Contact<\/strong><\/td><td>Mechanical scratching hazard (like glass dust).<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Ingestion<\/strong><\/td><td>Non\u2011toxic; passes through unabsorbed.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>PPE:<\/strong> N95 or P100 respirator (for dust), safety goggles, work gloves.<br><strong>Firefighting:<\/strong> Non\u2011combustible.<br><strong>Storage:<\/strong> Normal dry storage; no special atmosphere.<br><strong>Disposal:<\/strong> Can be disposed as construction\/demolition waste; not hazardous.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">6. <strong>Environmental Impact<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Aluminum silicate is chemically inert and does not leach toxic ions or alter pH. Its environmental footprint comes mainly from mining and the energy used in firing kilns.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">7. <strong>Comparison with Other Aluminum Compounds<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-center\" data-align=\"center\">Compound<\/th><th class=\"has-text-align-center\" data-align=\"center\">Formula<\/th><th class=\"has-text-align-center\" data-align=\"center\">Primary Nature<\/th><th>Primary Application<\/th><\/tr><\/thead><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Aluminium Silicate<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Al\u2082SiO\u2085<\/td><td class=\"has-text-align-center\" data-align=\"center\">Refractory ceramic<\/td><td>Furnace bricks, spark plugs<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Aluminium Sulfate<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Al\u2082(SO\u2084)\u2083<\/td><td class=\"has-text-align-center\" data-align=\"center\">Soluble salt<\/td><td>Water purification<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Aluminium Hydroxide<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Al(OH)\u2083<\/td><td class=\"has-text-align-center\" data-align=\"center\">Amphoteric powder<\/td><td>Antacids, flame retardants<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">8. <strong>Frequently Asked Questions<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Q: Is this the same as the silica gel packets in shoe boxes?<\/strong><br>A: No. Those are pure silica (SiO\u2082). Aluminum silicate contains firmly bound alumina, making it much harder and non\u2011absorbent.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Q: Is kyanite jewelry safe to wear?<\/strong><br>A: Yes. Kyanite is a natural, insoluble crystal form of aluminum silicate \u2013 completely safe to touch and wear.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Q: Can I melt aluminum silicate in a backyard foundry?<\/strong><br>A: No. Backyard propane foundries typically reach 1200\u20111300\u202f\u00b0C. Aluminum silicate requires &gt;1800\u202f\u00b0C to melt. In fact, your furnace is likely lined with it to protect the steel shell.<\/p><div class=\"pai-ad\" style=\"min-height:250px;visibility:hidden;\"><span style=\"display: block; text-align: center; font-size: 10px; margin: 0 0 10px 0; color: #999999;\">Ads<\/span>\r\n<!-- Display-300x250-1 -->\r\n<ins class=\"adsbygoogle\"\r\n     style=\"display:inline-block;width:300px;height:250px\"\r\n     data-ad-client=\"ca-pub-3838168351244230\"\r\n     data-ad-slot=\"9933646018\"><\/ins>\r\n<script>\r\n     (adsbygoogle = window.adsbygoogle || []).push({});\r\n<\/script><\/div>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<div style=\"height:75px\" aria-hidden=\"true\" class=\"wp-block-spacer\"><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">9. <strong>Summary Data Sheet<\/strong><\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th class=\"has-text-align-center\" data-align=\"center\">Property<\/th><th class=\"has-text-align-center\" data-align=\"center\">Value<\/th><\/tr><\/thead><tbody><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Chemical Name<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Aluminum Silicate<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Mineral Names<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Andalusite, Kyanite, Sillimanite<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Formula<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Al\u2082SiO\u2085<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Appearance<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">White powder; colored mineral gems<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Melting Point<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">&gt;1850\u202f\u00b0C (transforms to mullite ~1450\u202f\u00b0C)<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Defining Trait<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Extreme refractoriness<\/td><\/tr><tr><td class=\"has-text-align-center\" data-align=\"center\"><strong>Primary Utility<\/strong><\/td><td class=\"has-text-align-center\" data-align=\"center\">Furnace bricks, spark plug insulators<\/td><\/tr><\/tbody><\/table><\/figure>\n<\/p><script>document.addEventListener(\"DOMContentLoaded\",function(){\n        if(window.innerWidth <= 768){\n            if (\"immediate\" === \"delay\") {\n                setTimeout(function(){document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\")},0);\n            } else if (\"immediate\" === \"scroll\") {\n                window.addEventListener(\"scroll\",function(){\n                    let s=window.scrollY\/(document.body.scrollHeight-window.innerHeight);\n                    if(s>0.1){\n                        document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\");\n                    }\n                });\n            } else {\n                document.querySelectorAll(\".pai-ad\").forEach(el=>el.style.visibility=\"visible\");\n            }\n        } else {\n            document.querySelectorAll(\".pai-ad\").forEach(el=>el.remove());\n        }\n    });<\/script>","protected":false},"excerpt":{"rendered":"<p>Aluminum silicate represents a family of naturally occurring minerals \u2013 andalusite, kyanite, and sillimanite \u2013 all sharing the same chemical formula but differing in crystal structure due to formation under different pressures and temperatures. Industrially, it is valued for its extreme refractoriness (heat resistance) and is used in spark plugs, kiln linings, and catalyst supports. &#8230; <a title=\"Aluminium Silicate (Al\u2082SiO\u2085): The Complete Guide\" class=\"read-more\" href=\"https:\/\/aluminiummagazine.com\/mag\/aluminium\/compounds\/aluminium-silicate-properties-ceramic-guide.html\" aria-label=\"Read more about Aluminium Silicate (Al\u2082SiO\u2085): The Complete Guide\">Read more<\/a><\/p>\n","protected":false},"author":12,"featured_media":17987,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4155],"tags":[4141,4142],"class_list":["post-17868","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-compounds","tag-aluminium-compounds","tag-aluminum-formula"],"_links":{"self":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts\/17868","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/users\/12"}],"replies":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/comments?post=17868"}],"version-history":[{"count":0,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/posts\/17868\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/media\/17987"}],"wp:attachment":[{"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/media?parent=17868"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/categories?post=17868"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aluminiummagazine.com\/mag\/wp-json\/wp\/v2\/tags?post=17868"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}