{"id":7889,"date":"2024-05-17T11:35:19","date_gmt":"2024-05-17T09:35:19","guid":{"rendered":"https:\/\/www.pasqualerobustini.com\/?page_id=7889"},"modified":"2024-05-17T11:35:19","modified_gmt":"2024-05-17T09:35:19","slug":"granati-e-silicati-di-alluminio","status":"publish","type":"page","link":"https:\/\/www.pasqualerobustini.com\/en\/geologia\/di-cosa-sono-fatti-i-magmi\/granati-e-silicati-di-alluminio\/","title":{"rendered":"Garnets and aluminum silicates"},"content":{"rendered":"

Another typical metamorphic mineral family are the Garnets<\/strong>. They are Nesosilicates, that is they are structured by isolated groups of SiO4<\/sub>4-<\/sup> tetrahedrons; in this case the groups are made of 3 tetrahedrons: (SiO4<\/sub>)3<\/sub>5-<\/sup>. Aluminum is often found bonded to those groups to form the typical Garnet radical: Al2<\/sub><\/span>(SiO4<\/sub>)3<\/sub><\/span>3-<\/sup>, but ferric iron (III) is also common in Andradite, as chrome is in Uvarovite. This radical may also bond magnesium, iron and calcium.<\/p>\n\n\n\n\n\n\n\n\n\n\n
\n
\n<\/td>\n<\/tr>\n
Mg<\/td>\n<\/td>\nFe<\/td>\n<\/td>\nMn<\/td>\n<\/td>\nFe3+<\/sup><\/td>\n<\/td>\nAl<\/td>\n<\/td>\nCr<\/td>\n<\/tr>\n
\"geomin-piropo\"<\/a><\/td>\n<\/td>\n\"geomin-almandino\"<\/a><\/td>\n<\/td>\n\"geomin-spessartite\"<\/a><\/td>\n<\/td>\n\"geomin-andradite\"<\/a><\/td>\n<\/td>\n\"geomin-grossularia\"<\/a><\/td>\n<\/td>\n\"geomin-uvarovite\"<\/a><\/td>\n<\/tr>\n
Mg3<\/sub>Al2<\/sub><\/span>(SiO4<\/sub>)3<\/sub><\/span><\/td>\n<\/td>\nFe3<\/sub>Al2<\/sub><\/span>(SiO4<\/sub>)3<\/sub><\/span><\/td>\n<\/td>\nMn3<\/sub>Al2<\/sub><\/span>(SiO4<\/sub>)3<\/sub><\/span><\/td>\n<\/td>\nCa3<\/sub>Fe2<\/sub><\/span>(SiO4<\/sub>)3<\/sub><\/span><\/td>\n<\/td>\nCa3<\/sub>Al2<\/sub><\/span>(SiO4<\/sub>)3<\/sub><\/td>\n<\/td>\nCa3<\/sub>Cr2<\/sub><\/span>(SiO4<\/sub>)3<\/sub><\/span><\/td>\n<\/tr>\n
Pirope<\/strong><\/td>\n<\/td>\nAlmandine<\/strong><\/td>\n<\/td>\nSpessartite<\/strong><\/td>\n<\/td>\nAndradite<\/strong><\/td>\n<\/td>\nGrossular<\/strong><\/td>\n<\/td>\nUvarovite<\/strong><\/td>\n<\/tr>\n
<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<———<\/td>\n<\/td>\nCalcic Garnets<\/td>\n<\/td>\n———><\/td>\n<\/tr>\n
\n
\n<\/td>\n<\/tr>\n
<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Another group of nesosilicates is an important indicator of a metamorphic rock’s formation temperature: the aluminum silicate<\/strong> Al2<\/sub>SiO5<\/sub>. It exists in three polymorphs, never to be found together in the same rock, since they are stable at different pressure and temperature conditions: Andalusite forms at low pressure (LP) but variable temperatures; Cyanite only forms at high pressure (HP > 4 Kbar); Syllimanite forms at high temperature (HT) but variable pressure.<\/p>\n\n\n\n\n\n\n
HP<\/td>\nLP<\/td>\nHT<\/td>\n<\/tr>\n
\"geomin-cianite\"<\/a><\/td>\n\"geomin-andalusite\"<\/a><\/td>\n\"geomin-sillimanite\"<\/a><\/td>\n<\/tr>\n
Al2<\/sub>SiO5<\/sub><\/td>\n<\/tr>\n
Cyanite<\/strong><\/td>\nAndalusite<\/strong><\/td>\nSyllimanite<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

\"geomin-Silicate-double-tetrahedra-3D-balls\"In some cases, the tetrahedron groups are formed by Si2<\/sub>O7<\/sub><\/span>6-<\/sup> pairs (left) and are called Sorosilicates. In the Epidote<\/strong> group the tetrahedrons are bonded to calcium, ferric iron and aluminum, and also to a SiO4<\/sub><\/span> group. Most common Epidotes are the Zoisite (orthorombic) and the Clinozoisite (monocline):<\/p>\n\n\n\n\n\n\n\n\n
\n
\n<\/td>\n		<\/td>\n<\/tr>\n
Fe3+<\/sup><\/td>\n<\/td>\nAl<\/td>\n<\/td>\n<\/tr>\n
\"geomin-epidoto\"<\/a><\/td>\n<\/td>\n\"geomin-zoisite\"<\/a><\/td>\n<\/td>\n<\/tr>\n
Ca2<\/sub>(Al,Fe)3<\/sub>O(SiO4<\/sub><\/span>)(Si2<\/sub>O7<\/sub><\/span>)(OH)<\/td>\n<\/td>\nCa2<\/sub>Al3<\/sub>O(SiO4<\/sub><\/span>)(Si2<\/sub>O7<\/sub><\/span>)(OH)<\/td>\n<\/td>\n<\/tr>\n
Epidote<\/strong><\/td>\n<\/td>\nZoisite<\/strong><\/td>\n<\/td>\n<\/tr>\n
\n
\n<\/td>\n		<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

<\/p>","protected":false},"excerpt":{"rendered":"

Another typical metamorphic mineral family are the Garnets. They are Nesosilicates, that is they are structured by isolated groups of SiO44- tetrahedrons; in this case the groups are made of 3 tetrahedrons: (SiO4)35-. Aluminum is often found bonded to those groups to form the typical Garnet radical: Al2(SiO4)33-, but ferric iron (III) is also common […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1728,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/pages\/7889"}],"collection":[{"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/comments?post=7889"}],"version-history":[{"count":1,"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/pages\/7889\/revisions"}],"predecessor-version":[{"id":7890,"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/pages\/7889\/revisions\/7890"}],"up":[{"embeddable":true,"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/pages\/1728"}],"wp:attachment":[{"href":"https:\/\/www.pasqualerobustini.com\/en\/wp-json\/wp\/v2\/media?parent=7889"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}