Basalt that has been streamlined as it passed though the air. For
more images of volcanic bombs follow this link - BOMBS
The dark rock is BASALT and within the gas pockets minerals have
grown. This mineral (from Horseshoe Dam, AZ) is Natrolite.
Porphyritic Andesite - This rocks represents a transition from the
extrusive (fine grained) to the intrusive (coarse grained). The feldspar
crystals, that are easily seen with the unaided eye, developed deep beneath the
surface of the Earth. In this plutonic realm that crystallized slowly and
became large. Then, the still fluid magma flowed to the surface and became
a lava flow. The remaining molten rock then cooled quickly to produce the
fine grained groundmass of andesite. Porphyries thus represent two
distinct cooling stages.
Pumice floating in a beaker of water.
A chunk of Pumice.
Rainbow Obsidian
Spessartine Garnet in Rhyolite from Arizona.
Obsidian with flow lines
Topaz Rhyolite from Topaz Mountain, Utah
