t it is open
to objection since it had earlier been applied to several other species,
and is also now used as a group name for meteoric irons. Chalybite
crystallizes in the rhombohedral system and is isomorphous with calcite;
like this it possesses perfect cleavages parallel to the faces of the
primitive rhombohedron, the angles between which are 73 deg. 0'.
Crystals are usually rhombohedral in habit, and the primitive
rhombohedron r {100} is a common 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 or fine
granular texture; also in botryoidal or globular (sphaerosiderite) and
oolitic forms. When compact and mixed with much clay and sand it
constitutes the well-known clay ironstone. Chalybite is usually
yellowish-grey or brown in colour; it is translucent and has a vitreous
lustre. Hardness 3-1/2; sp. gr. 3.8. The double refraction ([omega] -
[epsilon] = 0.241) is stronger than that of calcite. When pure it
contains 48.2% of iron, but this is often partly replaced isomorphously
by manganese, magnesium or calcium: the varieties known as oligon-spar
or oligonite, sideroplesite and siderodote contain these elements
respectively in large amount. These varieties form a passage to ankerite
(q.v.) and mesitite, and all are referred to loosely as brown-spar.

[Illustration: Crystal of Chalybite.]

Chalybite is a common gangue mineral in metalliferous veins, and
well-crystallized specimens are found with ores of copper, lead, tin,
&c., in Cornwall, the Harz, 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 Coal Measures of England and the United States, and the
oolitic iron ore of the Cleveland district in Yorkshire forms beds in
the Lias. The mineral is occasionally found as concretionary masses
(sphaerosiderite) in cavities in basic igneous rocks such as dolerite.
(L. J. S.)

CHAMBA, a native state of India, within the Punjab, amid the Himalayas,
and lying on the southern border of Kashmir. It has an area of 3216 sq.
m. Pop. (1901) 127,834. The sanatorium of Dalhousie, though within the
state, is attached to the district of Gurdaspur. Chamba is entirely
mountainous; in the e