Scapolite

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scapolite

[′skap·ə‚līt]
(mineralogy)
A white, gray, or pale-green complex aluminosilicate of sodium and calcium belonging to the tectosilicate group of silicate minerals; crystallizes in the tetragonal system and is vitreous; hardness is 5-6 on Mohs scale, and specific gravity is 2.65-2.74. Also known as wernerite.

Scapolite

 

a group of silicate minerals consisting of the solid-solution series 3NaAlSi3O8 NaCl-3CaAl2Si2O8-(CaCO3, CaSO4). The end sodium member of the series is called maria-lite, and the end calcium member, meionite. The intermediate members of the series include dipyre (20–50 percent of the meionite component) and mizzonite (50–80 percent).

Structurally, scapolite consists of a framework of quaternary ring-shaped groups of aluminosilicate tetrahedrons. Na+ and Ca2+ ions are housed in the smaller vacancies, and ClScapolite, and Scapolite anions are accommodated in the larger ones. Scapolites form either acicular crystals of the tetragonal system or solid granular aggregates. They have a hardness on Mohs’ scale of 5–6, and the density is 2,500–2,780 kg/m3. Colors are white, yellow, blue (glaucolite), or pink.

Scapolites are widespread in calcium-rich metamorphic rocks (marbles, gneisses, granulites, greenschist), skarns, and hydrothermally altered (through plagioclase minerals) basic magmatic rocks. Large scapolite crystals are found in the USSR in the Baikal Region (Sliudianka and Malaia Bystraia rivers) and in the Il’men Mountains in the Urals. They are also found in Finland, Norway, Madagascar, and Canada. Scapolites are used as industrial stones (glaucolite). Kaolins are formed through the weathering of scapolites.

A. S. MARFUNIN