LISTING
DESCRIPTION
Kyanite, whose name derives from the Greek word kuanos
sometimes referred to as "kyanos", meaning deep blue, is a typically
blue silicate mineral, commonly found in aluminium-rich metamorphic pegmatites and/or sedimentary
rock. Kyanite in metamorphic
rocks generally indicates pressures higher
than 4 kilobars.
DETAILED
DESACRIPTION
Although
potentially stable at lower pressure and low temperature, the activity of water
is usually high enough under such conditions that it is replaced by hydrous
aluminosilicates such as muscovite,
pyrophyllite,
or kaolinite.
Kyanite is also known as disthene, rhaeticite and cyanite.Kyanite is a member of the aluminosilicate series, which also includes the polymorph andalusite and the polymorph sillimanite. Kyanite is strongly anisotropic, in that its hardness varies depending on its crystallographic direction. In Kyanite, this anisotropism can be considered an identifying characteristic.
At temperatures above 1100 °C kyanite decomposes into mullite and vitreous silica via the following reaction: 3(Al2O3·SiO2) → 3Al2O3·2SiO2 + SiO2. This transformation results in an expansion.[4]
Uses of kyanite
Kyanite
is used primarily in refractory
and ceramic products, including porcelain
plumbing fixtures and dishware.
It is also used in electronics, electrical insulators and abrasives.Kyanite has been used as a semiprecious gemstone, which may display cat's eye chatoyancy, though this use is limited by its anisotropism and perfect cleavage. Color varieties include recently discovered orange kyanite from Tanzania.[citation needed] The orange color is due to inclusion of small amounts of manganese (Mn3+) in the structure.[5]
Kyanite is one of the index minerals that are used to estimate the temperature, depth, and pressure at which a rock undergoes metamorphism.
Notes for identification
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 of 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.
Occurrence
Kyanite
occurs in gneiss,
schist,
pegmatite,
and quartz veins resulting from moderate to high-pressure regional metamorphism
of principally pelitic rocks. It occurs as detrital grains in sedimentary
rocks. It occurs associated with staurolite,
andalusite,
sillimanite,
talc,
hornblende,
gedrite,
mullite
and corundum.
PRICE FOR ALUMINA
CONTENT
$1.7/KG OR $0.77/IB
For more information:
mobile: +2348039721941
contact person: emeaba uche
e-mail: emeabau@yahoo.com
No comments:
Post a Comment