| Named after the town of Andalusia,
Spain, where Andalusite was first found, it varies from pale
yellow to dark green, brown and greenish red. Like
Alexandrite, Andalusite changes in color depending on which
way you look at it, and on how it's lighted. The same stone
can appear green, red or even have flashes of yellow.
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 included in the crystal. These
inclusions are arranged in regular symmetrical shapes.
It is mainly a collectors item, and has not seen wide use in
the jewelry trade. The name comes from the Greek "chiastos"
meaning "X-marked". It was used as an amulet by early Christens.
Color is white, red, brown, orange and green. Luster
is vitreous. Transparency crystals are transparent to
translucent. Chemistry: Al2 SiO5, Aluminum Silicate 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 Enhancements: None |
