|
PRECIOUS STONES
|
141
|
||
|
|
|||
|
GARNET
Has many varieties and as many names.
The
crystallization is isometric, and it occurs in rhombic dodecahedrons
and trapezohedrons, sometimes variously modified. It is found nearly
all over the world.
Hardness
varies from 6, that of demantoid, the softest variety, to 7.5 to 8,
that of uwarowite (or ouvarovite), the hardest; the red varieties range
from 7 to 8; specific gravity, 3.4 to 4.3; brittle.
Lustre vitreous; transparent to opaque.
Cleavage parallel to faces of dodecahedron, rather indistinct; fracture uneven.
Refraction single (index, 1.74 to 1.815); pyrope, highest; essonite, lowest; electric by heat and friction.
The
composition is very varied, but is a compound of three or four
silicates in different proportions, the various combinations giving
rise to the many shades of color in which it occurs. The green
demantoid contains a large proportion of iron.
Most
varieties fuse to a brown or black glass. Uwarowite fuses with borax
to a green glass. Demantoid under blow-pipes fuses to a black bead.
Color, red in all shades, green, orange, yellow, etc. The reds tend to brownish, yellowish, and purple tints.
Large stones are usually cut brilliant and en cabochon; small, rose-cut. L* Symbolizes power, grace, victory, January.
Names by which the Garnet Varieties are known
Almandine..........Wine-red; hardness, 7-1/4 ', specific
gravity, 4.1 to 4.3.
|
|||
|
|
|||