Margarite Locality: Dobrava, Unterdrauburg, Slovenia — Photo: Slashme · CC BY 4.0
Margarite
Also known as: Brittle mica.
The calcium 'brittle mica' — a white-to-pinkish phyllosilicate of metamorphosed aluminous rocks.
Intro adapted from Wikipedia (CC BY-SA).
Margarite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaAl₂Si₂Al₂O₁₀(OH)₂.
It crystallizes in the monoclinic crystal system (space group Cc). It is a member of the Mica, Clay structural group.
Key properties: Mohs hardness 3.5–4.5; specific gravity 2.99–3.08; typically white or pink or gray; White streak; Pearly on cleavage, vitreous on lateral faces luster; optically biaxial.
IMA symbol Mrg, IMA status: approved, named in 1821.
From low- to medium-grade metamorphic rocks, as in emery deposits, chlorite and mica schists, and glaucophane-bearing rocks.
It is found associated with Corundum, diaspore, tourmaline, staurolite, glaucophane, chlorite, magnetite, spinel, andalusite, calcite, quartz.
Its name comes from the Greek for pearl, for its pearly luster on cleavage.
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