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Kyanite, whose name derives from the Greek word kyanos, meaning blue, is a typically blue silicate mineral, commonly found in aluminium-rich metamorphic pegmatites and/or sedimentary rock. Kyanite is a diagnostic mineral of the Blueschist Facies of metamorphic rocks. Kyanite is a member of the aluminosilicate series, which includes the polymorph andalusite and the polymorph sillimanite. Kyanite is strongly anisotropic, in that its hardness varies |
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depending
on its crystallographic direction. While this is a
feature of almost all minerals, in kyanite this
anisotropism can be considered an identifying
characteristic.
Kyanite's elongated, columnar crystals are usually a
good first indication of the mineral, as well as its
color (when the specimen is blue). Associated minerals
are useful as well, especially the presence of the
polymorphs or staurolite, which occur frequently with
kyanite. However, the most useful characteristic in
identifying kyanite is its anisotropism. If one suspects
a specimen to be kyanite, verifying that it has two
distinctly different hardnesses on perpendicular axes is
a key to identification. some people use kyanite
