Margarite

This article refers about a member of the mica group, and should not be confused with "margarita".

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	09.EC.30
Crystal system	monoclinic
Identification
Color	flesh pink
Crystal habit	platy
Cleavage	basal
Mohs scale hardness	4

Margarite is a calcium rich member of the mica group of the phyllosilicates with formula: Ca Al₂(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.

References

Wikimedia Commons has media related to Margarite.

Deer, W.A., R.A. Howie, and J. Zussman (1963) Rock-forming minerals, v. 3, Sheet Silicates, p. 95-98.
Mindat with location data
Webmineral data
Mineral Data Publishing PDF

Phyllosilicates

Serpentine group	Antigorite Chrysotile Lizardite Népouite

Clay mineral group	Allophane Chlorite¹ Dickite Halloysite Illite Kaolinite Montmorillonite Nacrite Nontronite Palygorskite Saponite Sepiolite Serpentine¹ Talc

Mica group	Biotite Glauconite Lepidolite Margarite Muscovite Phlogopite

Chlorite group	Chlorite

1. Serpentine and chlorite are sometimes considered clay minerals

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