Vitrophyre. See [Obsidian] and [Vitrophyre].
Volcanic Ash ([Pumicite])
[Volcanic ash] deposits, which also are known as [pumicite], are loose and powdery. They are made up mostly of material that is thrown into the air when volcanoes erupt. If a volcano erupts with a violent explosion, the nearby rocks are blown into powder. Molten [lava] also is hurled into the air, where some of it immediately cools to become tiny bubbles and particles of glass. The winds may carry some of this fine material far away before depositing it.
Deposits of [volcanic ash] are white, bluish, greenish, yellowish, or grayish, and some of them glisten like snow in the sunlight. They feel rough and gritty. When examined under a microscope, this material shows the tiny curved and sharp-cornered particles of the broken [volcanic] glass. Deposits of volcanic ash may also contain [clay], silt, [sand], or other impurities.
Volcanoes, which may have been located in the Davis Mountains and in other areas of west Texas and in northern Mexico, erupted during [Tertiary] time. The [volcanic] ash that we find at the surface today in some of the Tertiary [formations] in Texas could have come from these volcanoes. Tertiary [volcanic ash] deposits occur in the Texas [Gulf Coastal Plain] (such as in Brazos, Fayette, Karnes, Polk, Starr, Trinity, and other counties) and in the [Trans-Pecos] country of west Texas.
[Volcanic ash] deposits of [Quaternary] ([Pleistocene]) age, which are less than a million years old, are found in a number of counties on the Texas [High Plains]. Farther to the east, ash deposits occur in Baylor, Dickens, Kent, and Wilbarger counties. This volcanic ash may have come from a volcano that erupted in northern New Mexico during Quaternary time.
[Volcanic ash] or [pumicite] has several commercial uses. Some is used to make pozzolan cement, and some is used in sweeping compounds, cleansing and scouring powders, and abrasive soaps. Pumicite has been mined in Dickens, Scurry, Starr, and several other counties of Texas.
Wad. See [Manganese Minerals].
Wood Opal. See [Opal].