Azurite. See [Copper Minerals].
Barite
[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.
[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.