THE MINERAL ANDALUSITE

  • Chemistry: Al2 SiO5, Aluminum Silicate
  • Class: Silicates
  • Subclass: Nesosilicates
  • Uses: in the manufacture of spark plugs etc, as a gemstone and as mineral specimens.
  • Specimens

Andalusite is named for its type locality of Andalusia, Spain. It 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 other minerals.

A unique variety of andalusite is called "chiastolite". It contains black or brown clay and/or carbonaceous material (often graphite) inclusions in the crystal. These inclusions are arranged in regular symmetrical shapes - especially prized when 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.
This Site Awarded
Available ANDALUSITE specimens:
ANDALUSITE specimen AND-11
$ 45.00 -40% = $ 27.00
Dims: 1x1x1in (3x3x2cm) .... Wt: 1.02oz (29.0g) .... Loc: Jenipapo mine, Itinga, Minas Gerais, Brazil
Two crystals of andalusite are intergrown here. They have a nearly rectangular cross section, are brown, and slightly transparent.
no photo
AND-11
$ 27.00
no photo
ANDALUSITE specimen AND-12
$ 30.00 -40% = $ 18.00
Dims: 1.04x0.84x1.06in (2.65x2.14x2.69cm) .... Wt: 0.95oz (27.0g) .... Loc: Jenipapo mine, Itinga, Minas Gerais, Brazil
This appears to be a single crystal of andalusite, slightly distorted and quite irregular in shape as the growth stopped at different levels for different steps of the crystal. It is brown, and slightly transparent in some areas although the bulk of the crystal appears opaque.
no photo
AND-12
$ 18.00
no photo
see this List of ALL specimens including SOLD ones

 

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