Mineral description : Magnesite

Picture pending, magnesite from Horstmannaho, Autokumpu area, Finland.

Magnesite crystal from Altemark, Mo i Rana, Norge.
Hard to see, covered in chlorite, but it's half the piece.

Mineral class Carbonates : calcite group

Chemical formula MgCO₃

Crystal system Trigonal

Habitus Often massive or grainy. Crystals rhomoedric or prismatic.

Cleavage Romboedric, complete.

Hardness 3.5-4.5

Density 3.0-3.2 (rising with iron content)

Color Usually colorless or white when pure, gray yellow or brownish nuances when iron is present.

Streak White

Luster Glas to pearly.

Description Used as base for making cement and fireproof bricks.

Occurance Magnesite is less common than calcite and is rarely created as sedimentary rock.
It often occurs as metasomatic altered rocks, in magnesium rich rock altered by carbonate rich solutions, or carbonatic rock altered by magnesium rich solutions.

Associates Talc and serpentinites.

Notes Magnesite looks like calcite but is almost not affected by cold hydrochloric acid. Reacts strongly with hot hydrochloric acid.
Breunnerite is a name on a magnesite with 5-30% iron

Locations Magnesite have been mined in some places along the fjelds.

Tarrekaise, northern Lappland.
Äpartjåkko, northern Lappland.
Also common in talc around peridotites.

Laisholm, Hemavan. As light brown crystals in talc.
Horstmannaho, Finland. As light yellow crystals in talc.
Altemark, Norway. In talc and chlorite around a peridotite.

To carbonates index.
Mineral group index.
Main index.

If you have some questions, suggestions or comments you are welcome to write me a line or two.

axelsson@acc.umu.se

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Last changed : 1998-03-07

Mineral class	Carbonates : calcite group
Chemical formula	MgCO₃
Crystal system	Trigonal
Habitus	Often massive or grainy. Crystals rhomoedric or prismatic.
Cleavage	Romboedric, complete.
Hardness	3.5-4.5
Density	3.0-3.2 (rising with iron content)
Color	Usually colorless or white when pure, gray yellow or brownish nuances when iron is present.
Streak	White
Luster	Glas to pearly.
Description	Used as base for making cement and fireproof bricks.
Occurance	Magnesite is less common than calcite and is rarely created as sedimentary rock. It often occurs as metasomatic altered rocks, in magnesium rich rock altered by carbonate rich solutions, or carbonatic rock altered by magnesium rich solutions.
Associates	Talc and serpentinites.
Notes	Magnesite looks like calcite but is almost not affected by cold hydrochloric acid. Reacts strongly with hot hydrochloric acid. Breunnerite is a name on a magnesite with 5-30% iron
Locations	Magnesite have been mined in some places along the fjelds. Tarrekaise, northern Lappland. Äpartjåkko, northern Lappland. Also common in talc around peridotites. Laisholm, Hemavan. As light brown crystals in talc. Horstmannaho, Finland. As light yellow crystals in talc. Altemark, Norway. In talc and chlorite around a peridotite.