Marcasite

Real mineral · common · FeS₂

The same iron disulfide as pyrite, built orthorhombic instead of cubic, paler and far less stable: specimens crumble to powder and sulfuric acid in damp air. The marcasite of jewellery is almost always pyrite.

Identity

Formula

FeS₂

Chemical class

sulfide

Also known as

White iron pyrite

Crystallography

Crystal system

orthorhombic

Habits

tabular, bladed, nodular, botryoidal

Fracture

uneven

Physical properties

Mohs hardness

6

Density

4.89 g/cm³

Luster

metallic

Colors

bronze, light brass yellow, tin white

Streak

gray brownish black

Transparency

opaque

Geology

Origins

sedimentary, hydrothermal

Host rocks

shale, chalk, coal

Associated minerals

Pyrite, Galena, Sphalerite, Calcite

Geography

United Kingdom, France, USA

Classification

Rarity

common

Gem quality

No

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