hematite

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hematite

(hĕm`ətīt), mineral, an oxide of iron, Fe2O3, containing about 70% metal, occurring in nature in red to reddish-brown earthy masses and in steel-gray to black crystalline forms. Hematite that has a metallic luster is called specular hematite, or specular iron. The red powdered hematite is used as a pigment (ocherocher
, mixture of varying proportions of iron oxide and clay, used as a pigment. It occurs naturally as yellow ocher (yellow or yellow-brown in color), the iron oxide being limonite, or as red ocher, the iron oxide being hematite.
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) and as rouge in polishing. Hematite is the most important ore of iron. Extensive and richly productive deposits occur in the Lake Superior region (Michigan, Minnesota, and Wisconsin) and the Birmingham district (Alabama). The mineral is widely distributed throughout the world and is responsible for the red coloration of many sedimentary rocks. See limonitelimonite
or brown hematite
, yellowish to dark brown mineral, a hydrated oxide of iron, FeO(OH)·nH2O, occurring commonly in deposits of secondary origin, i.e., those formed by the alteration of minerals containing iron.
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Hematite

 

a widely distributed ferrous mineral, Fe203, containing up to 70 percent iron. Hematite is crystallized in a trigonal system. Its crystals are steel gray with a semimetallic shine. Depending on the mineral aggregate structures and the crystallic concretion shapes, a distinction is made among (1) hematite iron glance (macrocrystalline concretions); (2) ferrous mica (flaky aggregates); (3) ferrous rosette (crystal concretions reminiscent of corollas of dog rose); (4) red ironstone (dense red microcrystallic units); (5) kidney ore (red dense reniform conglomerations); and (6) martite (dense or porous ore formations). On the mineralogical scale, the hardness is 5.5-6; the density, 5,260 kg per cu m. The powder is cherry red in color. The melting point is 1594° C.

Together with magnetite, geothite, and quartz, hematite is formed in deposits of different genetic types and in various rocks, when the oxidizing potential of the medium is sufficiently high. Hematite ores are ferrous ores of great importance, being used for smelting cast iron and steel. Iron content in solid hematite ores fluctuates from 50 percent to 65 percent. The largest deposits are connected with the oldest Precambrian ferriferous quartzites (jaspilites).

In the USSR the Krivoi Rog hematite ore deposit (in the Ukrainian SSR), the Kursk Magnetic Anomaly, and the Urals and Siberian deposits are well known. The biggest deposits abroad are situated near Lake Superior, Birmingham, and elsewhere in the USA; in the state of Minas Gerais in Brazil; and in Canada (Labrador), India (states of Bihar, Orissa, and Madhya Pradesh), and several countries of Africa.

hematite

[′hē·mə‚tīt]
(mineralogy)
Fe2O3 An iron mineral crystallizing in the rhombohedral system; the most important ore of iron, it is dimorphous with maghemite, occurs in black metallic-looking crystals, in reniform masses or fibrous aggregates, or in reddish earthy forms. Also known as bloodstone; red hematite; red iron ore; red ocher; rhombohedral iron ore.
References in periodicals archive ?
This process results in characteristic red, hematitic nodules with a yellow, goethitic cortex.
* The grading downslope is a purplish-red to blue-green to brownish-green Hematitic zone that is the bulk of the orebody (about 75% overall); and
The Magcobar barite zone consisted of up to 15 meters of massive barite (averaging 85% BaS[O.sub.4]), underlain by hematitic and jasperoid bands and overlain by pyritic, dolomite breccias with minor galena and sphalerite (Taylor and Andrew, 1978).
The mineralisation is primarily pyrite with minor chalcopyrite (copper sulphide) accompanied by strong chlorite and in places siliceous and hematitic (jasperoidal) alteration.
Due to the lack of pedogenic features such as root channels and soil horizons, Pillans and Bourman (1996) concluded that the hematitic mottles in the Ochre Cove Formation formed by subsurface weathering associated with a fluctuating water-table below the active soil zone.
Rocko describes a series of pockets along a zone of contact between syenite and marble in the Valentine mine, these pockets lined primarily with hematitic quartz prisms to 10 cm long - and there are a few specimens, from miniature-size up to about 10 x 12 cm, showing these attractive, transparent red-dusted quartz crystals all by themselves in solid groups.
Active Mining Area Cutoff Grades (oz/st) Ore type Hematitic Siliceous Clay Crusher 0.013 0.016 0.009 ROM 0.007 0.007 NA
The following Paleocene Sangiali group represents Rakhi Gaj (Girdu member, glauconitic and hematitic sandstone; Bawata member, alternation of shale and sandstone), and Dungan (thick limestone with minor shale) formations;
The core of essentially barren hematite-quartz breccias is surrounded by complexly intermingled granitic and hematitic breccias about 1 km in width and extending almost 5 km in a NW-SE direction.