Kyanite belongs to the
class of silicates. Derived from Aluminum silicate, Kyanite
is polymorph with mineral andalusite & sillimanite i.e.
they have similar chemistry but different crystal structure.
Mineral kyanite has typical blue colour & wide variation
in hardness, which can be called its unique characteristics.
It's hardness may vary from 4-7.5 in the same specimen
crystal. Usually, Kyanite found in rocks that are formed in
high pressure conditions that is to say metamorphic rocks.
Although it has characteristic blue colour, Kyanite may be
green, yellow, white.
are three polymorphs of Al2SiO5: andalusite, kyanite and
sillimanite. These three minerals form in aluminous
metamorphic rocks. The temperature and pressure are what
determines which of these polymorphs will crystallize.
Kyanite is typically found in rocks that formed under
conditions of high pressure regional metamorphism. Kyanite
most often occurs in high pressure regionally metamorphosed
aluminous rocks and in the quartz veins that cut through
them, associated with quartz, muscovite, almandine garnet,
biotite, staurolite and corundum. It also occurs in some
kimberlite pipes and eclogites associated with pyrope garnet
and omphacite. The blue color in metamorphic kyanite is due
to trace amounts of Fe+2 and Ti+4 impurities substituting
for aluminum. The light blue color of kyanites found in
kimberlites is due to trace amounts of chromium.