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Glittering
Stones >> Semi
Precious Stones >> Opal
Semi Precious Stone Opal
The mineral opal is amorphous hydrated silica,
its water content sometimes being as high as 30%. Being amorphous
has no crystal form, occurring in its irregular
veins and masses. It has concordat fracture, hardness 5.5-6.5,
specific gravity 2.1-2.2, and a highly variable color. Opal ranges
from colorless through white, milky blue, gray, red, yellow, green,
and also brown and black. Often many of these colors could be
seen at once, caused by interference from minute cracks in the
opal which are normally filled with secondary silica and by thin
lamellae formed inside the opal during its solidification.
The term "opalescent" usually refers to this unusual
and beautiful type of color.
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Historical Facts Of Opal
| Refractive Index |
1.44 - 1.46 |
| Chemical Composition |
SIO2nH2O |
| Hardness |
5.5 - 6.0 |
| Density |
2.65 - 3.00 |
| Crystal Group |
Amorphous |
| Ocurrence |
Czechoslovakia, Mexico, Honduras, Australia, Brazil,
Tanzania |
| Types |
Milk opal, Resin opal, Wood opal, Menilite, Hyalite,
Glass-clear opal |
| Color information |
White, Green, Blue, Black, Red, Orange, Violet, Pink,
Grey, Yellow |
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Gemstone Opal Jewelry
| Opal Bracelet |
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| Opal Earrings |
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| Opal Necklace |
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| Opal Rings |
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