Andalusite varies in color from a pale yellowish-brown to a dark bottle-green, dark brown, or the most popular greenish-red. It has very strong and distinctive pleochroism. So, when turned, the same stone may appear red, green, and yellow. Large crystals may be vertically striated prisms with a square cross-section and pyramidal ends, but are rare.
More usual Andalusite stone is opaque, rod-like aggregates of crystals or waterworn pebbles. It is the pebbles that are usually cut as gemstones. Andalusite crystals may occur as opaque crystals with rhombic cross-sections. An opaque, yellowish-grey variety, chiastolite, occurs as long prisms. It makes a cross when cut and polished.
Occurrence
Andalusite usually occurs in pegmatites. Pebbles are found in the gem gravels of Brazil and Sri Lanka. Other localities include Australia, Canada, Russia, Spain, and the USA.
Andalusite Properties
- Specific Gravity: 3.16
- Refractive Index: 1.63-1.64
- Birefringence (DR): 0.010
- Luster: Vitreous
- Crystal Structure: Orthorhombic
- Composition: Aluminum silicate
- Hardness: 7½
Crystals Directory
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
W
Y
Z
Birthstone
January
February
March
April
May
June
July
August
September
October
November
December
