Prospector.
Two of the Texas [silver minerals], [argentite] and [cerargyrite], do not resemble silver at all. Argentite, a silver sulfide, is also called silver glance. It is a dark, lead-gray mineral with a metallic luster that weathers to a dull black. When you rub it across a [streak] plate, argentite gives a shiny, blackish to lead-gray streak. This mineral is soft enough to leave a mark on paper. It has a [specific gravity] of 7.3, and it is [sectile] enough to be cut smoothly (like soap) with a knife. In some places argentite is found as irregular masses or as a coating on rocks and other minerals.
Another silver mineral, [cerargyrite] (or horn silver) is a silver chloride. This mineral has a nonmetallic luster and is [transparent] to [translucent]. It resembles pearl-gray, white, greenish, or colorless wax. When exposed to the light it turns violet brown or black. Cerargyrite is soft—you can scratch it with a fingernail. Like [argentite], it is [sectile]. This mineral has a [specific gravity] of 5.5, and it commonly occurs as irregular masses and as crusts.
These [silver minerals] have been mined at a number of places in [Trans-Pecos] Texas. The largest silver mine in Texas, the Presidio mine, is located near Shafter in south-central Presidio County. It contains [argentite], [cerargyrite], and [native silver], along with [galena] and several other minerals. This mine is not open now, but in the years between 1885 and 1942, it produced a large amount of silver along with some lead and [gold]. There are several other lead-silver mines in this Shafter area, but none has produced as much as the Presidio mine.
In this mine, the [silver minerals] occur mostly in large, flat deposits in [Permian] [limestone] and other [sedimentary] rocks. The minerals are believed to have been deposited there—probably during [Tertiary] time—by solutions that came from hot [magma] far below the rocks. As they moved in along the layers of limestone, the solutions replaced portions of this rock with minerals containing silver, lead, and other [elements]. Later, water seeped into these deposits and dissolved some of the minerals. This dissolved material was then re-deposited, and it formed most of the minerals we now find there.
No silver is being mined in Texas at present, but it has, in the past, been produced from other Trans-Pecos mines. [Galena] that contains silver (called argentiferous galena) has been mined at the Bird mine at Altuda Mountain (about 14 miles east of Alpine) in northern Brewster County. It also has been obtained from mines in the Quitman Mountains and in the Eagle Mountains of Hudspeth County. Some [cerargyrite] has been mined at the Plata Verde mine near the Culberson-Hudspeth County line.
Several mines in the Van Horn area of Culberson and Hudspeth counties have produced silver along with copper. An important silver mine in this area is the now idle and flooded Hazel mine. (This mine is described with [copper minerals] on [p. 52].)
Smoky Quartz. See [Quartz].
Soapstone. See [Talc] and [Soapstone].
Specular Hematite. See [Hematite].