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.