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www.mineralgallery.co.za Minerals A-E |
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Aquamarine |
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Name
Aquamarine
Chemistry
Be3 Al2 Si6 O18
Uses
As mineral specimen and gemstone
Color
Blue
Hardness
7.5-8
Specific gravity
2.67-2.71
Streak
White
Crystals
(Hexagonal) Short or long prismatic; usually hexagonal, pyramidal, vertically striped, seldom tabular; intergrowth and surface growth; only occasional twinning
Accompanied by:
Quartz , feldspar, calcite, chrysoberyl, topaz, apatite, phenakite, fluorite wolframite and cassiterite
Similar to:
Chrysoberyl, apatite, spinel, brazilianite and tourmaline
Aquamarine belongs to the beryl group.
Its other cousins being the emerald (green), golden beryl (deep yellow to golden brown), morganite (pale rose to rose pink), heliodor (yellow to greenish yellow) and the goshenite (colorless). Large crystals have been found in Zimbabwe. Some of these have pools of good quality gem material. Namibia has also been a good source of perfect crystals with intense color. These are oftentimes found with black tourmaline.
Aquamarines are often heat treated to improve the color. When heat treated the undesirable yellow color changes to a more appealing blue.
Deep blue or Double blue is rarely found in large clean pieces anywhere in the world. Continuous production of such color is un-heard of, which keeps Zambian production in great demand. Lighter shades of this gem can be found in other countries (Nigeria, India) but popularity is growing for the deep blue green variety presently found in the Katete / Petauke area for its beautiful natural sea blue / green hue.
Zambian double blue is still readily sold overseas as 'Santa Maria L'Afrique' conjuring a mystique over its source. Prices for such gems have been known to reach over EUR 800 per carat
Uncut aquamarines are plentiful but relatively expensive, as would be expected of crystalline gemstone specimens. Large crystals of aquamarine are available on the open market and represent perhaps the largest raw gemstone specimens.
Most beryl is found in pegmatite dikes, where large crystals are intergrown with quartz and feldspar, but the emerald variety also occurs in altered limestone and in various metamorphic rocks. Crystal size ranges from tiny to enormous. A crystal weighing 200 tons was mined in Minas Gerais, Brazil, and crystals about 6 m (20 ft) long and 2 m (7 ft) across have been found in the Black Hills of South Dakota and in Albany, Maine. Common beryl has been mined for beryllium since 1925, notably in Brazil, where the largest deposits occur.
