Fuchsite

Fuchsite, also known as chrome mica, is a chromium (Cr)-rich variety of the mineral muscovite, belonging to the mica group of phyllosilicate minerals, with the chemical formula K(Al,Cr)₃Si₃O₁₀(OH)₂.^[2]

CategoryPhyllosilicate minerals

GroupMica group, dioctahedral mica group

FormulaK(Al,Cr)₃Si₃O₁₀(OH)₂

IMA statusVariety of muscovite

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Fuchsite
Verdite, a microcrystalline metamorphic rock, is composed mostly of green fuchsite. This specimen (6.5 cm across at its base), of Archean age, is from Barberton, Mpumalanga, South Africa
General
Category	Phyllosilicate minerals
Group	Mica group, dioctahedral mica group
Formula	K(Al,Cr)3Si3O10(OH)2
IMA status	Variety of muscovite
Crystal system	Monoclinic
Identification
Color	Light to medium green
Crystal habit	Curved aggregates
Cleavage	Perfect basal
Fracture	Uneven
Mohs scale hardness	2.5
Luster	Vitreous to pearly
Streak	White
Diaphaneity	Transparent to opaque
Specific gravity	2.8–2.9
Optical properties	Biaxial (–)
Refractive index	1.552–1.615
Birefringence	0.036
Dispersion	weak
References	[1]

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Trivalent chromium replaces one of the aluminium (Al) atoms in the general muscovite formula producing the apple green hue distinctive of fuchsite. It is often found in minute micaceous aggregates (with individual plates barely visible), as a major component of chromium rich phyllitic or schistose metamorphic rocks of the greenschist facies.

Verdite is a type of metamorphic rock made mostly of an impure, often multicolored, variety of fuchsite. It is used for ornamental carvings.

Fuchsite is named after the German chemist and mineralogist Johann Nepomuk von Fuchs.