Obsidian is a type of natural occurring glass formation produced when lava flows from a volcano and cools rapidly without sufficient time for crystalized growth to start.
Obsidian is commonly found within rhyolitic lava flows known as obsidian flows. Not a true mineral because as a glass it is not crystalline, no obsidian has been found that is older than Cretaceous age. Pure Obsidian is usually dark in appearance, though the color varies depending on the presence of impurities.
Iron and magnesium give the obsidian a dark green, brown or black color. In some stones, the inclusion of small, white clustered crystals of cristobalite in the black glass produce a snowflake pattern (snowflake obsidian). They may also contain patterns of gas bubbles that remained from the lava flow, these bubbles can produce interesting multicolor effects such as rainbow, velvet obsidian or a silver or golden sheen effect. The rarest obsidian comes from Glass Buttes, Oregon, the unique fire obsidian in a rainbow of bright colored layers of crystal magnetite.
The Origin Of Color - Fire Obsidian (The Canadian Mineralogist Vol. 4) PDF
Please Note: In some of the obsidian cabochon photos there are reflections and white specks (dust). These cabs are mirror polished and anything within a 360° radius is reflected like a mirror and every minute speck of dust flowing through the air is attracted like a magnet - these stones are gem quality specimens and have no flaws, you can also view our Testimonals.