Obsidian is volcanic glass--Lava cools quickly and produces a shiny-surface stone. Most obsidians are patent-leather black, but the obsidian from Guadalajara, Jalisco, Mexico, holds surprises: Included minerals add flashes of color and/or chatoyance as the stone is turned under strong light. In Rainbow Obsidian, these colors are striated, in stripes or layers. They are the result of the "depositional banding" or layering of various types of microscopic feldspar or mica crystals lined up just right within the glass. The colors in Velvet Obsidian show up in folded swirls of color, rather than rainbow stripes, and do resemble crushed velvet. I've categoried solid-color obsidians as velvets. The third, "sheen" group of obsidians are highly chatoyant--their gold and/or silvery rutiles flash metallic in the light. I am pleased to offer a selection of all three type of stones, many of which are beautifully carved by talented lapidarists in Mexico. Keep in mind that these are all changlings: They will present as black under low light or at certain angles, then reveal their colors and sheen under bright light. You can see photos of them under both conditions; just click on an image below. All have flat, soft-polish backs.