Also on these boards
There are many types of obsidian found through the world. This type, called fire obsidian, without a doubt is some of the most colorful and most rare of them all. It can rival the very finest of precious opal, and is found only in Glass Buttes, Oregon (on privately owned property). by James A. Miller
Green Obsidian.The translation into English of Natural History written by the elder Pliny of Greece shows a few sentences on the subject of a volcanic glass called Obsian, so named from its resemblance to a stone found in Ethiopia by Obsius (obsiānus lapis).