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CHALYBITE , a See also: mineral See also: species consisting of iron carbonate (FeCO3) and forming an important ore of iron
.
It was early known as spathose iron, spathic iron or See also: steel ore
.
F
.
S
.
Beudant in 1832 gave the name siderose (from viSrlpos, iron), which was modified by W
.
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 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 combination with the basal pinacoid are also frequent, giving crystals of octahedral aspect . The mineral often occurs in cleavable masses with a coarse orSee 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 colour; it is translucent and has a vitreous lustre
.
Hardness 31; sp. gr
.
3.8
.
The
See also: double 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, magnesium or 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 copper, See also: lead, 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 dolerite
.
(L
.
J
.
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