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CHALYBITE

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Originally appearing in Volume V05, Page 813 of the 1911 Encyclopedia Britannica.
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CHALYBITE , a See also:

mineral See also:species consisting of See also:iron carbonate (FeCO3) and forming an important ore of iron. It was See also:early known as spathose iron, spathic iron or See also:steel ore. F. S. See also:Beudant in 1832 gave the name siderose (from viSrlpos, iron), which was modified by W. See also:Haidinger in 1845 to siderite. Chalybite (from xh))ui//, XaXv(3os, See also:Lat. chalybs, steel) is of slightly later date, having been given by E. F. Glocker in 1847. The name siderite is in See also:common use, but it is open to objection since it had earlier been applied to several other species, and is also now used as a See also:group name for meteoric irons. Chalybite crystallizes in the See also:rhombohedral See also:system and is isomorphous with See also:calcite; like this it possesses perfect cleavages parallel to the faces of the See also:primitive rhombohedron, the angles between which are 730 0'. Crystals are usually rhombohedral in See also:habit, and the primitive rhombohedron r {loos is a common See also:form, the faces being often curved as represented in the figure.

Acute rhombohedra in See also:

combination with the basal pinacoid are also frequent, giving crystals of octahedral aspect. The mineral often occurs in cleavable masses with a coarse or See also:fine granular texture; also in botryoidal or globular (sphaerosiderite) and oolitic forms. When compact and mixed with much See also:clay and See also:sand it constitutes the well-known clay ironstone. Chalybite is usually yellowish-See also:grey or See also:brown in See also:colour; it is translucent and has a vitreous lustre. Hardness 31; sp. gr. 3.8. The See also:double See also:refraction ((a —E=o•241) is stronger than that of calcite. When pure it contains 48.2 % of iron, but this is often partly replaced isomorphously by See also:man- ganese, See also:magnesium or See also:calcium: the varieties known as oligon-spar or oligonite, sideroplesite and sidero- dote contain these elements respec- tively in large amount. These varieties form a passage to See also:ankerite Crystal of Chalybite. (9.v.) and mesitite, and all are referred to loosely as brown-spar. Chalybite is a common See also:gangue mineral in metalliferous See also:veins, and well-crystallized specimens are found with ores of See also:copper, See also:lead, See also:tin, &c., in See also:Cornwall, the Harz, See also:Saxony and many other places. It also occurs alone as large masses in 'veins and beds in rocks of various kinds.

The clay ironstone so extensively worked as an ore of iron occurs as nodules and beds in the See also:

Coal See also:Measures of See also:England and the See also:United States, and the oolitic iron ore of the See also:Cleveland See also:district in See also:Yorkshire forms beds in the See also:Lias. The mineral is occasionally found as concretionary masses (sphaerosiderite) in cavities in basic igneous rocks such as See also:dolerite. (L. J.

End of Article: CHALYBITE

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