Black Obsidian Round Coasters Uniqueness Guaranteed: Every item is one-of-a-kind, making them ideal for all projects or designs. Origin: India Quantity: set of 2 Size: 3"-5" Obsidian is not a gemstone but a kind of glass that forms when volcanic lava rapidly cools in the open air without forming any specific crystalline structures. Depending on the included minerals, obsidian can occasionally exhibit a gold, silver, or rainbow sheen when polished. Custom Requests: Have specific preferences? Leave a message with your order, and we'll do our best to accommodate your requests if possible. Handmade items vary in size, shape, and color when selected randomly (the highest quality items are chosen first). They'll be as beautiful as those in the photos.