Mineral description : Dolomite

Dolomite from Horsmanaho, Finland.
Dolomite from Innansjön.

Mineral class Carbonates, dolomite-ankerite group.
Chemical formula CaMg(CO3)2
Crystal system Trigonal
Habitus Romboedric crystals with curved surfaces {10/11}. Also as grainy masses.
Hardness 3.5-4
Density 2.8-2.9
Color usually colorless, but nuances in yellow, gray and pink.
Luster glas to pearly.
Description Dolomite is usually created through metasomatic transformation of calcite under appending of magnesium ions.
Dolomite can also be created through hydrothermal transformation of magnesium rich carbonate and silicate rocks. Together with dolomite, magnesite, serpentine, brucite and magnetite are also created. (As in Modum)
Occurance Dolomite is the main ingredience of dolomitic marble. It can also occur in hydrothermal veins, around mangane mines, and in some serpentinites.
Associates calcite, magnesite, serpentine, brucite, magnetite
Notes Dissolves slowly in cold hydrochloric acid, fast only as a pulver or in hot acid.
Named after the French geologist D Dolomieu (1750-1801).
Locations Dolomite is a common mineral in Sweden, often around ores as grainy masses. At some places as marble.
  • Sala silver mine, Västmanland.
  • In the skytt mine in Falun, as coarse grained masses.
  • Innansjön, Burträsk. as small yellow crystals in calcite.
  • In the mangan mines of Värmland.
  • The Dolomites mountains in Italy is mainly dolomite.
  • Modum in Norway.
  • Tangen/Stange Norway. As 1 cm crytals with ametist and pyrite in cracks in the grunnfjells gneiss.
  • Gjövik Norway. As small crystals in cracks in a black schist.
  • Fauske Norway. With pyrite, quartz, calcite, muscovite, rutil and chlorite.
  • Horsmanaho, Finland. As coarse crystalline masses in talc.

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Last changed : 1998-03-07