Formula: Ca(Fe2+,Mg)(CO3)2 Usually contains large amounts of Mg and sometimes Mn.

Species: Carbonates

Colour: Brown, white to grey, yellowish-brown, tan, fawn, greenish.

Lustre: Pearly

Hardness: 3½ – 4

Specific Gravity: 2.93 – 3.10

Crystal System: Trigonal

Member of: Dolomite Group, Ankerite-Dolomite Series, and the Ankerite-Kutnohorite Series.

Name: Named after Matthias Joseph Anker, Austrian mineralogist. It was commonly given the end-member formula Ca2FeMg(CO3)4; Hey (1955) actually used the name ferrodolomite for CaFe(CO3)2. The redefinition of the name means the majority of old specimens labelled “ankerite” are now considered to be ferroan dolomite, and true ankerite is quite rare.

Note: Most (unanalysed) “ankerite” specimens are actually Fe-bearing (ferroan) dolomite (Mg>Fe), because of nomenclature changes. The majority of alleged “ankerite” photos here actually depict Fe-rich dolomite (except for a relatively few analytically confirmed ankerites). Even the old so-called “type locality ankerite” from Erzberg, Styria, would not quite fit the modern definition.