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HAEMATITE, or HEMATITE

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Originally appearing in Volume V12, Page 804 of the 1911 Encyclopedia Britannica.
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HAEMATITE, or HEMATITE , a See also:mineral consisting of ferric See also:oxide (Fe203), named from the See also:Greek word 'alga, " See also:blood," in allusion to its typical See also:colour, whence it is called also red See also:iron ore. When crystallized, however, haematite often presents a dark colour, even iron-See also:black; but on scratching the See also:surface, the See also:powder of the streak shows the colour of dried blood. Haematite crystallizes in the See also:rhombohedral See also:system, and is isomorphouswith See also:corundum (Al203). The See also:habit of the crystals may be rhombohedral, pyramidal or See also:tabular, rarely prismatic. In fig. 1 the crystal, from See also:Elba, shows a See also:combination of the fundamental rhombohedron (R), an obtuse rhombohedron (s), and the hexagonal bipyramid (n). Fig. 2 is a tabular crystal in which the basal pinacoid (o) predominates. Haematite has no distinct cleavage, but may show, in consequence of a lamellar structure, a tendency to parting along certain planes. FIG. I. Crystallized haematite, such as that from the iron-mines of Elba, presents a See also:steel-See also:grey or iron-black colour, with a brilliant metallic lustre, sometimes beautifully iridescent.

The splendent surface has suggested for this mineral such names as specular iron ore, looking-See also:

glass ore, and iron glance (Ter oligiste of See also:French writers). The hardness of the crystallized haematite is about 6, and the specific gravity 5.2. The so-called " iron See also:roses " (Eisenrosen) of See also:Switzerland are rosette-like aggregates of hexagonal tabular crystals, from fissures in the gneissose rocks of the See also:Alps. Specular iron ore occurs in the See also:form of brilliant FIG. 2. metallic scales on many lavas, as at See also:Vesuvius and See also:Etna, in the See also:Auvergne and the See also:Eifel, and notably in the See also:Island of See also:Ascension, where the mineral forms beautiful tabular crystals. It seems to be a sublimation-product formed in volcanoes by the interaction of the vapour of ferric chloride and See also:steam. Specular haematite forms a constituent of certain schistose rocks, such as the Brazilian itabirite. In the See also:Marquette See also:district of See also:Michigan (See also:Lake See also:Superior) schistose specular ore occurs in important deposits, associated with a See also:jasper See also:rock, in which the ore alternates with bands of red See also:quartzite. Micaceous iron ore consists of delicate steel-grey scales of specular haematite, unctuous to the See also:touch, used as a lubricant and also as a pigment. It is worked in See also:Devonshire under the name of shining ore. Very thin laminae of haematite, blood-red by transmitted See also:light, occur as microscopic enclosures in certain minerals, such as carnallite and See also:sun-See also:stone, to which they impart colour and lustre.

Much haematite occurs in a compact or massive form, often mammillary, and presenting on fracture a fibrous structure. The reniform masses are known as See also:

kidney ore. Such red ore is generally neither so dense nor so hard as the crystals. It often passes into an earthy form, termed soft red ore, and when mixed with more or less See also:clay constitutes red ochre, ruddle or reddle (Ger. Rotel). The hard haematite is occasionally cut and polished as an ornamental stone, and certain kinds have been made into beads simulating black pearls. It was worked by the Assyrians for their engraved See also:cylinder-See also:seals, and was used by the gnostics for amulets. Some of the native tribes in the See also:Congo See also:basin employ it as a material for axes. The hard fibrous ore of See also:Cumberland is known as See also:pencil ore, and is employed for the burnishers used by bookbinders and others. See also:Santiago de Compostela in See also:Spain furnishes a considerable See also:supply of haematite burnishers. Haematite is an important ore of iron (q.v.), and is extensively worked in Elba, Spain (See also:Bilbao), Scandinavia, the Lake Superior region and elsewhere. In See also:England valuable deposits occur in the Carboniferous See also:Limestone of See also:west Cumberland (See also:Whitehaven district) and See also:north See also:Lancashire (See also:Ulverston district).

The hard ore is siliceous, and See also:

fine crystallized specimens occur in association with smoky See also:quartz. The ore is remarkably See also:free from See also:phosphorus, and is consequently valued for the See also:production of See also:pig-iron to be converted into See also:Bessemer steel. (F. W.

End of Article: HAEMATITE, or HEMATITE

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HAEMATOCELE (Gr. aiya, blood, and rd7X17, tumour)

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