Barite, barium sulfate, is a fairly common mineral in Texas. It has a
glassy or a pearly luster, and it is transparent to translucent. Barite
is colorless, white, brownish, bluish, yellowish, or reddish. When
rubbed across a streak plate, it gives a white streak. It is not
extremely hard—you can scratch it with a pocket knife, although not with
a fingernail.
Barite is distinctive because of its weight and cleavage. It cleaves in
three directions, and some cleavage fragments are flat or platy. For a
mineral with a nonmetallic luster, barite is heavy—it has a specific
gravity of 4.5.
[Illustration: Barite cleavage fragment from west Texas.]
Barite commonly occurs as prism-shaped and as flat crystals, as granular
masses, as cleavable masses, and as rounded masses called _nodules_. In
Texas, some of it was deposited in sedimentary rocks by underground
waters. As the waters seeped through these rocks, mineral matter came
out of solution to form the barite. Some of the barite in Texas also
formed from solutions that came from hot magmas.
A number of barite deposits have been found in Texas, but many of them
are small. Barite occurs in Precambrian metamorphic rocks in Gillespie
and Llano counties, in Pennsylvanian shale in Brewster County, in
Permian shales in Baylor and Taylor counties, and in Permian limestones
in Culberson County. It is found in Triassic red shales in Howard County
and in Cretaceous sedimentary rocks in Brewster, Brown, Hudspeth, Jeff
Davis, Kinney, and Val Verde counties. In Live Oak County, barite occurs
in Tertiary bentonitic clays. Barite is being mined from a deposit in
the Seven Heart Gap area northeast of Van Horn in Culberson County.
Barite is used in a number of ways. It is a source of barium chemicals,
and it also is powdered and used as an ingredient in paint. The oil
industry uses large amounts of barite. In drilling for oil by the rotary
method, water and muds are pumped down the hole to aid drilling. Barite
is added to these drilling fluids to make them heavy, since
high-pressure gases are not as likely to blow heavy fluids out of the
hole.