1910–1911
Britannica 11th
Encyclopaedia Britannica · 11th edition
ANKERITE, a member of the mineral group of rhombohedral carbonates. In composition it is closely related to dolomite, but differs from this in having magnesia replaced by varying amounts of ferrous and manganous oxides, the general formula being Ca(Mg,Fe,Mn) (CO8)2. Normal ankerite is Ca2 MgFe(C03)4. The crystallographic and physical characters resemble those of dolomite and chalybite. The angle between the perfect rhombohedral cleavages is 73° 48', the hardness 3! to 4, and the specific gravity 2-9 to 3-1; but the…
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- Vol. 2, pp. 58-58