Photos of rocks with glass present. Glass is formed when moulten rock cools too quickly for minerals to grown. Click on any photo for a larger image. Some of the larger images may be on other web sites and will open in a new window.

Obsidian sample with banding

glass-hs_001.Black rhyolite obsidian with flow banding marked with lines of tiny white bubbles, Glass Mountain, CA, USA. 8 cm long pocket knife for scale.



Obsidian sample with banding

glass-hs_002.Flow banding in glassy volcanic rock, Santorini, Greece. The photo is approximately 15 cm across.



Obsidian sample with banding

glass-hs_003. Black obsidian from Obsidian Cliff, Yellowstone National Park, WY, USA. Smithsonian exhibit (NMNH 72853). The photo is approximately 15 cm across.



Colorful glass surface of basalt flow

glass-hs_004. Colorful glass surface of pahoehoe basalt lava flow, Kilauea Volcano, HI, USA. The photo is approximately 10 cm across.