Glittering Stones >> Semi
Precious Stones >> Obsidian
Semi Precious Stone Obsidian
Top stone is obsidian, below that it is pumice and in
lower right hand is rhyolite (light color)Obsidian is one type of naturally
occurring glass, which produced from volcanoes (igneous rock) when a fluid
felsic lava cools rapidly and then freezes
without sufficient time for crystal growth, for example
by flowing into a body of the water. It consists mainly of SiO2 (silicon
dioxide), 80% or more. Obsidian is a mineral-like, but not a true mineral
because it is not a crystalline. Its composition is very similar to that
of granite and also rhyolite. It is sometimes also classified as a mineral
aid.
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Historical Facts of Obsidian
| Hardness |
5 - 6 |
| Chemical Composition |
70–75% SiO2, plus MgO, Fe3O4 |
| Density |
2.6 |
| Luster |
Vitreous |
| Color |
Black, Gray, Dark green, Red, Yellow, Pink |
| Occurrence |
Newberry Volcano, Medicine Lake Volcano of western North America, Sierra Nevada of California, Yellowstone National Park and other western US states |
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Gem Jewelry Obsidian
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