Ankerite is a calcium , manganese of the group of rhombohedral carbonates with formula: Ca(Fe,Mg,Mn)(CO3)2. In composition it is closely related to dolomite , but differs from this in having magnesium replaced by varying amounts of iron(II) and manganese. It forms a series with dolomite and kutnohorite
The crystallographic and physical characters resemble those of dolomite. The angle between the perfect rhombohedral cleavages is 73° 48', the hardness is 3.5 to 4, and the specific gravity is 2.9 to 3.1. The color is white, grey or reddish to yellowish brown.
Ankerite occurs with siderite in metamorphosed ironstones and sedimentary banded iron formations. It also occurs in carbonatites minerals and as a product of hydrothermal It is one of the minerals of the dolomite-siderite series, to which the terms brown-spar, pearl-spar and bitter-spar have been historically loosely applied.
It was first recognized as a distinct species by W. von Haidinger in 1825, and named for Matthias Joseph Anker , an Austrian
It has been found in Western Tasmania, in mines in Dundas, Tasmania.