Shop Obsidian tumbles, carvings, jewellery and polished pieces in black, snowflake, mahogany, gold-sheen and other varieties. Obsidian is a natural volcanic glass formed when lava cools rapidly, creating a smooth surface and sharp fracture. Traditionally associated with protection, grounding and honest self-reflection, it is popular for pocket stones and bold decorative shapes. Natural sheen and pattern vary with the variety.