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
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