what is Andalusite? Where is it found?

Answer 1

Andalusite is a polymorph with two other minerals; kyanite and sillimanite. A polymorph is a mineral that shares the same chemistry but a different crystal structure with another, or other, minerals. A unique variety of andalusite is called "chiastolite". It contains black or brown clay and/or carbonaceous material inclusioned in the crystal. These inclusions are arranged in regular symmetrical shapes. Usually they are in the form of a cross or X.

PHYSICAL CHARACTERISTICS:
Color is white, red, brown, orange and green.
Luster is vitreous.
Transparency crystals are transparent to translucent.
Crystal System is Orthorhombic; 2/m2/m2/m
Crystal Habits include prismatic crystals with a square cross section terminated by a pinacoid. also massive and granular.
Cleavage is good in two directions.
Fracture is splintery to subconchoidal.
Hardness is 7.5
Specific Gravity is approximately 3.15+ (above average)
Streak is white.
Associated Minerals are cordierite, biotite, feldspars, quartz, kyanite and sillimanite.
Other Characteristics: dark inclusions produce cruciform shapes in the variety, chiastolite. Index of refraction is 1.632-1.638.
Notable Occurrences include Andalusia, Spain; Austria; California, USA and China.
Best Field Indicators are crystal habit, color, inclusions (if present) and hardness.

Answer 2

Andalusite is an aluminium nesosilicate mineral with the chemical formula Al2SiO5.

The variety chiastolite commonly contains dark inclusions of carbon or clay which form an X or a cross in section.

A clear variety first found in Andalusia, Spain can be cut into an interesting gemstone.[1] Faceted andalusite stones give a play of red, green, and yellow colors that resembles a muted form of iridescence, although the colors are actually the result of unusually strong pleochroism.


Occurrence
Andalusite is a common regional metamorphic mineral which forms under high pressure and/or temperature. The minerals kyanite and sillimanite are polymorphs of andalusite, each occurring under different temperature-pressure regimes and are therefore rarely found together in the same rock. Because of this the three minerals are a useful tool to help identify the pressure-temperature paths of the host rock in which they are found.

It was first reported from Andalucia, Spain in 1789.

Details
Crystallographic system Orthorhombic
Colours Brown, green, pink, violet and red varieties
Lustre
Hardness 7.5
Specific gravity 3.13 - 3.17
Refractive index 1.641-1.648
cleavage 3
Twinning Lamellar
Pleochroism Clear to patchy pink

Related minerals:

Kyanite
Sillimanite
Chiastolite


Andalusite is found in phyllites, schists and gneisses and associated quartz veins. It indicates relatively low pressure metamorphism of aluminum-rich rocks, such as shales.

Answer 3

Andalusite - Al2SiO5 i.e an aluminium silicate. it is characterised by nearly square prisms and has a hardness of 7 and a half. it has a vitreous luster and is flesh red, reddish brown, olive-green. It is formed typically in the contact aureoles of igneous intrusions in argillaceous rocks. Notable locaities are in andalusia, spain; the Austrian Tyrol; Minas Gerais, Brazil. In the US - the White Mountains near Laws, California and in Delaware County, Pennsylvania.

Answer 4

can be found in Spain, makes for a cool looking gemstone