Precious Fire Obsidian 48 x 38 mm. 134 cts. Precious Fire obsidian is a material which only occurs on Glass Buttes in central Oregon. It has extremely thin layers of minerals which break up light into spectacular, shifting colors. This material is not the same as "rainbow" obsidian, or other sheen obsidians. Recently, some doublet and triple stones have hit the market which incorporate a layer of Paua abalone shell to imitate the effect.