Darth Vader Black Obsidian Crystal Carving

Obsidian is a dark-colored volcanic glass formed when molten lava cools quickly. It is usually black but colored varieties range from brown to red. Obsidian is an igneous rock that's rich in silica (65–80%) and low in water. It has a chemical composition similar to rhyolite. Obsidian is usually black, but can also be brown, red, green, yellow, orange, or blue. The presence of hematite (iron oxide) produces red and brown varieties, and gas bubbles may create a golden sheen. Obsidian has a smooth, glassy texture. Obsidian has a conchoidal fracture, which means it breaks with smooth, curved surfaces that have a shell-like shape. Obsidian is slightly harder than window glass, with a Mohs scale hardness of 5–6. Obsidian is found in volcanic regions, such as the Mountain West, Southwest, California, Oregon, and Washington State. In the Black Rock Desert of western Utah, volcanic eruptions about 2.5 million years ago produced obsidian. Obsidian has been used for arrowheads, cutting tools, jewelry, and experimentally as surgical scalpel blades. Obsidian can be used as a hands-on aid in geology or earth science classes.