|
Occurrence
Olivine forms the main constituent of peridotites, and
also occurs in basalts and in crystalline limestone. The gem quality
olivine is also found in meteorites. In Burma, it is found in the Ruby
Mines area near Bernardmyo, where there are a number of exposures of
peridotite. Griesback mentions its occurrence in Afghanistan in a
basalt. But most of the gem quality stones come from the island of St.
John, off the coast of Egypt in the Red Sea. Other localities for gem
peridote are Burma, Ceylon, Queensland, Brazil and New Mexico.
Industry Some
small scale mining is done near Bernardmyo, Burma, and the stones are
sold locally along with other semi-precious stones in Mogok. It sells
for a rupee per carat.
Chapter XXI QUARTZ
Introduction
QUARTZ
is one of the most abundant minerals and the most common. It has many
varieties, which could be utilized for ornamental purposes. It occurs
in every type of rock, e.g. igneous, sedimentary or metamorphic, and
has both crystalline and amorphous forms with many attractive
varieties. It is one of the most important semiprecious stones. It is
found in rocks of all geological ages. It also fills cracks and
crevices and is the most important constituent of sands and gravels. It
has also been known from very ancient times. Flint, one of its
varieties, was known to primitive man, who made implements out of it
and also knew to produce sparks and then light his fire.
Quartz crystallizes in the hexagonal system in good prismatic crystals, the faces being horizontally striated and
140
|
||
|
|
||