[Specular hematite] from Carrizo Mountains, Hudspeth County, Texas.
Most metallic [hematite] is too hard for a pocket knife to scratch, but [quartz] or a steel file will scratch it. Hematite is fairly heavy, for it has a [specific gravity] of 5.26. This mineral has no [cleavage], but some specimens show three directions of [parting] that are almost at right angles to each other. A great help in identifying hematite is the dark reddish-brown [streak] it leaves when you rub it across a streak plate.
Some [hematite] occurs as rounded masses that resemble kidneys or bunches of grapes (then called kidney ore); it also is found as flat crystals. Most of the Texas hematite occurs as [granular] or compact masses. One of these [massive] varieties is composed of shiny scales or plates and is called micaceous or [specular hematite]. This variety has been found in Hudspeth County and in northeastern Mason County. Hematite also commonly occurs as cementing material in many Texas sandstones.
Some [hematite] is formed by the alteration of [magnetite], another iron mineral. This hematite is known as [martite], and some of it still has the crystal shape (an [octahedron] or a [dodecahedron]) that belonged to the magnetite. Most of the hematite found in the [Llano uplift] area of central Texas is believed to be altered magnetite. In this central Texas area, some [massive], [granular] martite has been mined at the Gamble prospect, a few miles southeast of Fredonia in northeastern Mason County, where it occurs as layers in [Precambrian] [gneiss].
Small deposits of [hematite] occur in other parts of Texas, too. Some of the west Texas localities include Sierra Blanca, the Quitman Mountains, and the Carrizo Mountains of Hudspeth County and the area around Shafter in Presidio County.
Hollandite. See [Manganese Minerals].
Hyalite. See [Opal].
Jasper. See [Quartz].
Kaolin. See [Clay].