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Tanzanite
Idocrase: Sometimes called vesuvianite, this mineral
occurs in fine crystals throughout the world. A massive
green or yellow-green variety. that closely resembles
jade is known as Californite. Faceted gems are bright
and beautiful, though rare, and the color range is enormous
¬colorless, pale yellow, yellow-green, green, brownish-green,
pale blue violet, and brown.
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The
hardness is 61/2, with indistinct cleavage and good
toughness. Gemmy material comes from Canada, Italy,
Pakistan Switzerland, and Africa. |
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lolite:
lolite is the gem name of the mineral cordierite, which is
a silicate of aluminum and magnesium. The hardness is 7-71/2,
with fair toughness due to a good cleavage. lolite is easily
recognized by its intense ¬trichroism: colorless, light
blue, and sapphire-blue, and that blue color has led to the
misnomer "water sapphire." Gems are usually cut
so only the blue color is seen, but a stone viewed from the
side will appear gray . Inclusions of an iron mineral sometimes
give stones from Sri Lanka reddish color. Localities include
India, Brazil, Burma, Norway, Finland and the Malaga say Republic.
Lolite is inexpensive and often turns up in parcel of sapphires.
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Tanzanite |
| Tanzanite
Kornerupine:
This is an extremely rare gem sought by collectors,
um ally appearing in shades of green and brown.
A variety rich in chromium has a pleasing apple-green
color, and yellowish stones from Canada a ¬known.
Some cat's-eyes are also known. The hardness is
61/z and most ¬gems come from Sri Lanka, Burma,
and the Malaga say Republic. Manganotantalite:
This very rare gem material is soft (6-6','2)
are cleaves easily, so cut gems are highly prized
by collectors and can ! expensive. The color is
dark brownish-red.
Proustite: More important to mineral collectors
for its fine crystal ¬Proustite is a silver
arsenic sulfide that occurs in a striking blood-red
crimson color. Cut gems are very rare but very
lovely. The hardness low, 21/2 on the Mohs scale,
so faceted gems are suitable only for collections.Rhodochrosite:
A manganese carbonate mineral, Rhodochrosite is
- in face table crystals. The hardness is low
(3-4) and cleavage is excel I , in three directions,
because Rhodochrosite is very similar in structure
calcite. But the striking pink or rose-red color
provides extremely beautiful faceted gems. Such
stones are usually under ten carats in weight.
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Massive
banded Rhodochrosite occurs in quantity in Argentina
where it makes up a substantial portion of a carbonate
cave. T stalactites and stalagmites in this cave
are pink and white Rhodochrosite -¬rather
than the more commonly seen calcite. Cabochons
of pattern, Rhodochrosite are popular among gem
hobbyists, and rough material available in quantity. |
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Scapolite:
Little known to the gem trade but very beautiful when cut,
Scapolite occurs in fine transparent crystals in colors including
color less, yellow, pink, green, and violet-blue. The hardness
is 51h-6 w - perfect cleavage present, so cut gems are delicate.
Fibrous inclusions Scapolite produce a fine cat's-eye effect,
or a chatoyancy similar to that of moonstone. Principal localities
are Burma, the Malaga say Republic Brazil, Siberia, and Canada.
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