2.1" Spiderweb Obsidian Cabochon

Obsidian is a natural volcanic "glass" that is formed when molten rock cools so quickly that the atoms don't have enough time to arrange themselves into crystals. To form obsidian, the composition of the lava must be high in silica. Depending on the minerals present within this lava along with the cooling rate, a variety of colorful bands, spots, or swirls can appear once the lava has solidified. Pure obsidian is often a solid black color, but impurities can result in small color variations throughout.

Obsidian was an important material for many ancient people. It was used for making tools, weapons, jewelry, and decorative items. It was a major barter material for Native Americans. Its conchoidal fracturing creates extremely sharp edges when it is broken, which made it ideal for making knives, scrapers, arrowheads, and spearpoints. It is even occasionally used today to produce surgical scalpels, since the edges can be several times sharper (only 3 nanometers wide) than blades produced from steel.