As with other forms of obsidian, rainbow obsidian is both rock and glass. However, this isn’t the same kind of glass that’s used in your nice new French doors. It’s far more badass ...

In addition to black, colors reported atop the cliff include brown, red, mahogany, gray and green. In Idaho, west of Yellowstone, Bear Gulch has a comparable high-quality obsidian, although it is ...

Obsidian is a black, often translucent rock. Volcanic eruptions sometimes ooze out magma that turns into this natural glass as it cools. Obsidian is hard, durable and can be worked to a razor ...