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.

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

Gem Jewelry Obsidian