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Lapis Lazuli
Lapis
is sometimes used as an alternative December birthstone. Lapis
is actually a rock made up of several different minerals, usually lazurite,
hauyne, sodalite and nosean, all members of the sodalite group of minerals.
Also present are calcite and pyrite in varying percentages. The finest Lapis is
considered to be a solid, deep blue with minimal white calcite spots and an
attractive sprinkling of golden pyrite. Lapis derives it's name from the
Persian word lazhward meaning blue. In ancient times, it was called sapphirus ,
a name which is now applied to our Sapphire. Powdered Lapis is the basis for
the pigment ultramarine, the deep blue color essential to an artist's palette.
The production of synthetic ultramarine has fortunately alleviated the need to
grind up natural Lapis Lazuli. Lapis has been
highly prized as an ornamental stone for over 6000 years. The Lapis mines high
above the Kokeha Valley in northeastern Afghanistan were ancient even when
visited by Marco Polo in 1271! Perhaps because deep blue Lapis with its flakes
of golden Pyrite resembles an evening sky dotted with sparkling stars, it was
long regarded as a cure for melancholy (the "blues"), and as an
amulet against the spirits of darkness. The cultures of ancient Mesopotamia
traded Lapis far and wide, regarding it at least as highly as gold. The
Egyptians were equally as fond of the stone and nobles such as King Tutankhamen
were interred with great stores of Lapis goods.
Some care against scratching and chipping should be taken when wearing Lapis.
Never clean in an ultrasonic cleaner.
TREATMENT: Commonly dyed
MOHS HARDNESS: 5-6 (depending on purity)
CHEMICAL COMPOSITION: (Na,Ca) 8 (Al,Si) 12 O 24 (S,So) 4
REFRACTIVE INDEX: 1.50
(The angle light is bent traveling through a gemstone)
DENSITY (SPECIFIC GRAVITY): 2.7-2.9
(The number of times heavier a gemstone is compared to water)
PRINCIPAL SOURCES: Afghanistan
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