Mineral description : Marcasite

Marcasite crystals in calcite from Kvinnestatorp.

Another piece of marcasite crystals in calcite from Kvinnestatorp.

Mineral class	Sulphides : Pyrite - Marcasite group.
Chemical formula	FeS2
Crystal system	Orthorombic.
Habitus	Common as striated tabular crystals, often curved. Usual in cockscomb formed crystals. Also as radiating rounded aggregates and balls.
Cleavage	Distinct with uneven fracture.
Hardness	6-6.5
Density	4.8-4.9
Color	Light brass colored. Often with a tarnished surface covered with rust.
Streak	Greenish black.
Luster	Metallic.
Description
Occurance	Commonly in low tempered hydrothermal veins. Also created in sedimentary rocks.
Associates	In hydrothermal veins, calcite, flourite and other sulphides.
Notes	The color is lighter than pyrite.
Locations	Occurs mainly in the younger part of the Swedish bedrock. Skåne, Öland and Gotland is good huntingground for balls of marcasite. In the Siljan area in many limestone quarries (Solberga, Osmundsberg, Kullsberg...). As crystals in calcite filled cracks with flourite and as concretions in slate.

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