|
280 PRECIOUS STONES.
|
||
|
|
||
|
fracture
is sub-conchoidal; it shows two cleavages, neither very distinct. The
crystals belong to the orthorhombic system, and are often twinned in
crossed forms ; hence the name. It occurs in crystalline rocks as a
product of contact metamorphism, and is often associated with Garnet
and Tourmaline. In chemical composition it is a conrplex silicate of
iron, magnesium and aluminium. It occurs in
|
||
|
|
||
|
|
||
|
|
||
|
schist
at Monte Campione in Switzerland, and with Corundum in Macon County in
North Carolina, in the United States. When used as a gem it is cut en cahochon.
481. Serpentine.
It
is rather questionable if the material used for the production of
plaques, vases, and other similar ornamental objects should not be
regarded rather as a rock than as a
|
||
|
|
||