Fuchsite, also known as chrome mica, is a
chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal.
Chromium metal is valued for its high corrosion resistance and hard ...
(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 extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...
group of
phyllosilicate minerals, with the chemical formula .
chromium replaces one of the
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
(Al) atoms in the general muscovite formula producing the apple green hue distinctive of fuchsite. It is often found in minute
micaceous aggregate
Aggregate or aggregates may refer to:
Computing and mathematics
* collection of objects that are bound together by a root entity, otherwise known as an aggregate root. The aggregate root guarantees the consistency of changes being made within the ...
s (with individual plates barely visible), as a major component of chromium rich
phyllitic or
schist
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes ...
ose
metamorphic 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 vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic ...
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
Sectility is the ability of a mineral to be cut into thin pieces with a knife. Minerals that are not sectile will be broken into rougher pieces when cut. Metals and paper are sectile.
Sectility can be used to distinguish minerals of similar appea ...
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 various minerals through the ability of harder material to scratch softer material.
The scale was introduced in 1812 by ...
. Fuchsite
fluoresces lime green under long wave
UV light
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
. Fuchsite's radioactivity due to its
potassium
Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmos ...
(K) content is barely detectable.
References
{{Reflist
External links
webmineral.com - Muscovite/Fuchsite
Phyllosilicates