Margarite

Margarite
Margarite from the Wright Mine, Chester Emery Mines, Chester, Hampden County, Massachusetts, USA. Size: 4.8 x 3.4 x 2.6 cm.
General
Category	Micas (phyllosilicates)
Formula (repeating unit)	CaAl2(Al2Si2)O10(OH)2
Strunz classification	9.EC.30
Crystal system	Monoclinic
Crystal class	Domatic (m) (same H-M symbol)
Space group	Cc
Identification
Color	flesh pink
Crystal habit	platy
Cleavage	basal
Mohs scale hardness	4
References

Margarite is a calcium rich member of the mica group of the phyllosilicates with formula: CaAl₂(Al₂Si₂)O₁₀(OH)₂. It forms white to pinkish or yellowish gray masses or thin laminae. It crystallizes in the monoclinic crystal system. It typically has a specific gravity of around 3 and a Mohs hardness of 4. It is translucent with perfect 010 cleavage and exhibits crystal twinning.

It occurs commonly as an alteration product of corundum, andalusite and other aluminous minerals. It has been reported as forming alteration pseudomorphs of chiastolite along with muscovite and paragonite. The margarite in this occurrence forms preferentially along the dark graphite rich inclusions with the chiastolite crystals.