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Tanzanite
Benitoite: One of the rarest and most beautiful gems,
it was first discovered in 1906. The only significant
locality is in southern California Gems may be colorless
and pink, but most commonly are sapphire - blue.
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The
dispersion of Benitoite is equal to that of diamond,
and stones cut to diamond angles and proportions may
look like blue diamond, The hardness is about 6-61/2
and tenacity is poor, but the beautiful color and dispersion
make Benitoite a most desirable gem. |
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Unfortunately
very little material exists, and cut stones over one carat
are consider( large and rare. Most existing cut Benitoite
are round brilliant gems. TI largest cut stones weigh less
than 15 carats.
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Tanzanite |
| Tanzanite
Brazilianite:
This phosphate mineral was first discovered in
Brazil 1944, happily in large, beautiful crystals
that somewhat resemble Chrysoberyl in color. The
hardness is only 51/z and the cleavage excellent,
so cut Brazilianite are too delicate to wear:
But the strong ¬yellow color is attractive
and large rough is available. Gem material, comes
only from Brazil, and cut gems can easily be distinguished
fro similar-appearing stones by standard gemological
tests.
Calcite: One of the most common minerals on earth,
calcite is calcium and makes up the rocks known
as limestone and marble. In massive, as marbles,
attractive banded material is cut for ornamen¬tal
building facings, as well as tabletops and carvings.
Calcite cur in a wide range of colors and sometimes
in large, transparent crystals.
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The
hardness is only 3 and cleavage is excellent in
three so gems are delicate and very difficult
to facet. Few stones are available even for collectors,
because the cost of material is too low e faceting
effort seem worthwhile. Yet the price per carat
may ,cause of cutting problems. |
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Cup
rite is copper oxide, and until 1974 was not really well a
gem material. Then a single pocket of large, transparent as
found in South West Africa, some of which can yield gems weighing
more than 100 carats. The hardness is only it the rich blood-red
color is spectacular. Collectors have snapped these stones
almost as quickly as they are cut, for the supply is very
limited.
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