Fuchsite, also known as chrome mica, is a

chromium Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium ...

(Cr)-rich variety of the mineral muscovite, belonging to the

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

group of phyllosilicate minerals, with the chemical formula . Trivalent chromium replaces one of the

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

(Al) atoms in the general muscovite formula producing the apple green hue distinctive of fuchsite. It is often found in minute

micaceous Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is co ...

aggregates (with individual plates barely visible), as a major component of chromium rich phyllitic or

schist Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced ''schistosity'' (named for the rock). This means that the rock is composed of mineral grains easily seen with a l ...

ose

metamorphic Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

rocks of the greenschist facies. Verdite is a type of

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

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.

Properties

Fuchsite crystallizes in the

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

crystal system. Common colour 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 The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by the Ger ...

. Fuchsite fluoresces lime green under long wave UV light. Fuchsite's radioactivity due to its

potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...

(K) content is barely detectable.

References

{{Reflist

External links

webmineral.com - Muscovite/Fuchsite
Phyllosilicates Mica group