1911 Encyclopædia Britannica/Chalybite

CHALYBITE, a mineral species consisting of iron carbonate (FeCO₃) and forming an important ore of iron. It was early known as spathose iron, spathic iron or steel ore. F. S. Beudant in 1832 gave the name siderose (from σίδηρος, iron), which was modified by W. Haidinger in 1845 to siderite. Chalybite (from χάλυψ, χάλυβος, Lat. chalybs, steel) is of slightly later date, having been given by E. F. Glocker in 1847. The name siderite is in 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 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° 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