Mineral description : Ankerite

Chemical formula CaFe(CO3)2
Hardness 3.5
Density 3.2
Color Light yellow to brown.
Crystal form Trigonal. Romboedric crystals or grainy masses.
Luster .
Description A rare mineral in Sweden. Occurs as crystals with quarts and calcite or as veins in some sulphide mines.
Habitat .
Alternative name Brunspat
Associates Quartz and calcite.
Notes Reacts with cold hydrochloric acid under release of gas, not as violent as calcite.
The density of ankerite separatest it from dolomite (2.8-2.9) and siderite (3.7-3.9).
After heavy firing, ankerite and siderite becomes magnetic, dolomite and calcite does not.
If a carbonatic sample is wetted with a weak acid solution of K3Fe(CN)6, some carbonates gets a blue color (Turnbulls blue) : calcite none, dolomite none, ankerite light blue, siderite dark blue.
Locations The best locations are :
  • Knolle mine, Ånimskogs socken, Älvsborgs län. As crystals in a mix of quarts and calcite.
  • Pahtavaara sulphide mine, Jukkasjärvi, Lappland. As veins.

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axelsson@acc.umu.se
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Last changed : 1998-03-07