Fuchsite

File:Verdite (microcrystalline fuchsite metamorphite) South Africa.jpg

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

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 following formula: K(Al,Cr)₂(AlSi₃O₁₀)(OH)₂.

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 an impure often multicolored variety of fuchsite used for ornamental carvings.

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

Properties

Fuchsite crystallizes in the monoclinic crystal system. Common color of the mineral is pale green to emerald green depending on the amount of Cr substitution. The micaceous crystals are flexible and slightly sectile with a hardness of 2-2.5 on the Mohs scale. Fuchsite fluoresces lime green under long wave UV light. Fuchsite's radioactivity due to its potassium (K) content is barely detectable.

References

• webmineral.com - Muscovite/Fuchsite