In composition it is closely related to dolomite, but differs from this in having magnesium replaced by varying amounts of iron(II) and manganese.

[3] It was first recognized as a distinct species by Wilhelm von Haidinger in 1825, and named for Matthias Joseph Anker (1771–1843) of Styria, an Austrian mineralogist.

[3] In 19th-century mineralogy, as well as in mining and among geologists, ankerite and its close analogues from the dolomite series were more often known by the capacious, expansive name of ″brown spar″.

[6]: 34  This is partly because this mineral is the extreme (with the highest content of divalent iron ions) member of the dolomite-ankerite isomorphic series, as a result of which dirty-brown varieties of dolomite, contaminated with impurities, could also be encountered under the name of brown spar.

[2] 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.