UT Permanent Collection - murphotos

Vesicular Basalt, Brewster County, Texas

Basalt is an aphanitic (fine-grained) igneous rock with generally 45-55% silica (SiO2) and less than 10% feldspathoid by volume, and where at least 65% of the rock is feldspar in the form of plagioclase. Dissolved magma gases form bubbles when erupted resulting in this characteristic texture pitted with many cavities (known as vesicles) at its surface and inside. Chemically this is actually a Trachyandesite.
Locality: outcrops along Texas FM 2627 near the Black Gap WMA.
Mineralogy: Little or no free quartz, dominated by alkali feldspar and sodic plagioclase along with one or more of the following mafic minerals: amphibole, biotite or pyroxene.
Specimen size: 12.5 cm long x 9 cm tall x 5 cm thick
Specimen weight: 578 grams
Collection ID:
Specimen in the permanent collection of the Jackson School of Geosciences, University of Texas at Austin.

BasaltTrachyandesiteBrewsterCounty201509305 inches x 3.5 inches x 1.5 inches578 gramsBrewster CountyVesicular BasaltRockextrusiveigneouslava