Today’s deskcrop comes from the Black Rock Desert of central Utah. It is a piece of snowflake obsidian. The Utah Geological Survey has a great write up of the origin of this rock and a field guide to the locality. You’ll notice the distinctive conchoidal fracture of obsidian catching the light nicely in the upper right portion of this sample. Also note that this sample comes from very near the spot where I collected the bread-crust rhyolite sample that was featured back in January.
Explore this and all of my 2010 Deskcrops and Outcrops in Google Earth!