HAEMATITE, or HEMATITE  , a mineral consisting of ferric oxide (Fe203), named from the Greek word 'alga, " blood," in allusion to its typical colour, whence it is called also red iron ore . When crystallized, however, haematite often presents a dark colour, even iron-black; but on scratching the surface, the powder of the streak shows the colour of dried blood . Haematite crystallizes in the rhombohedral system, and is isomorphouswith corundum (Al203) . The habit of the crystals may be rhombohedral, pyramidal or tabular, rarely prismatic . In fig . 1 the crystal, from Elba, shows a 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 steel-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-

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

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 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 cylinder-seals, and was used by the gnostics for amulets . Some of the native tribes in the Congo basin employ it as a material for axes . The hard fibrous ore of Cumberland is known as pencil ore, and is employed for the burnishers used by bookbinders and others . Santiago de Compostela in Spain furnishes a considerable supply of haematite burnishers . Haematite is an important ore of iron (q.v.), and is extensively worked in Elba, Spain (Bilbao), Scandinavia, the Lake Superior region and elsewhere . In England valuable deposits occur in the Carboniferous Limestone of west Cumberland (Whitehaven district) and north Lancashire (Ulverston district) .

The hard ore is siliceous, and

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