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Aqualite is a very rare mineral of the eudialyte group, with formula (H 3 O) 8 (Na,K,Sr) 5 Ca 6 Zr 3 SiSi(Si 24 O 66)(OH) 9 Cl. [2] [3] The formula given does not show the presence of cyclic silicate groups. The original formula was extended to show the presence of silicon at both M3 and M4 sites, according to the nomenclature of the eudialyte ...
Kentbrooksite is a moderately rare mineral of the eudialyte group, [2] with chemical formula (Na,REE) 15 (Ca,REE) 6 Mn 3 Zr 3 NbSi[(Si 9 O 27) 2 (Si 3 O 9) 2 O 2]F 2 ·2H 2 O. [3] This extended formula shows the presence of cyclic silicate groups and dominance of Si at the M4 site, according to the nomenclature of the eudialyte group. [4]
Feklichevite is a rare mineral of the eudialyte group with the formula Na 11 Ca 9 (Fe 3+,Fe 2+) 2 Zr 3 NbSi(Si 3 O 9) 2 (Si 9 O 27) 2. [3] [2] The original formula was extended to show the presence of cyclic silicate groups and presence of silicon at the M4 site, according to the nomenclature of eudialyte group. [4]
With two shared oxides bound to each silicon, cyclic or polymeric structures can result. The cyclic metasilicate ring Si 6 O 12− 18 is a hexamer of SiO 3 2-. Polymeric silicate anions of can exist also as long chains. In single-chain silicates, which are a type of inosilicate, tetrahedra link to form a chain by sharing two oxygen atoms each.
Given sufficient time, rainwater can dissolve even a highly resistant silicate-based mineral such as quartz. [13] Water breaks the bonds between atoms in the crystal: [14] The overall reaction for the dissolution of quartz results in silicic acid. SiO 2 + 2H 2 O → H 4 SiO 4. Another example of a silicate-based mineral is enstatite (MgSiO 3).
Zirsilite-(Ce) is a very rare mineral of the eudialyte group, with formula (Na, ) 12 (Ce,Na) 3 Ca 6 Mn 3 Zr 3 NbSi(Si 9 O 27) 2 (Si 3 O 9) 2 O(OH) 3 (CO 3)·H 2 O. [2] [3] The original formula was extended to show the presence of cyclic silicate groups and the presence of silicon at the M4 site, according to the nomenclature of the eudialyte group. [4]
Cyclic SiS 2 has been reported to exist in the gas phase. [95] The phase diagram of silicon with selenium has two phases: SiSe 2 and SiSe. [96] Tellurium silicide is a semiconductor with formula TeSi 2 or Te 2 Si 3. [97]
Regular coordination is not always present: for example, it is not found in Ca 2 SiO 4, which mixes six- and eight-coordinate sites for Ca II. Soro-silicates, involving discrete double or triple tetrahedral units, are quite rare: metasilicates involving cyclic [(SiO n 3)] 2n− units of corner-abutting tetrahedra forming a polygonal ring are ...