Obsidian is formed when volcanic lava cools and is mainly composed of SiO2. Obsidian is natural volcanic glass and has been used as a gemstone since ancient times Shiny and polished obsidian stone in irregular pieces. Sourced from Mexico. | Disclaimer: This pin contains affiliate links, which means I may earn a commission, at no cost to you, if you make a purchase through my link. Black Obsidian Stone, Protection Stones, Energy Crystals, Ancient Times, Wicca, Crystal Healing, Emotions, Gemstones, Irregular