Marcasite
| Colour | Gold, Gray, White, Brown, Yellow |
|---|---|
| Mohs hardness | 6–6.5 |
| Lustre | Metallic |
| Streak | Dark-grey to black |
| Crystal system | Orthorhombic |
| Transparency | Opaque |
| Cleavage | Cleavage: {101}, rather distinct; {110} in traces |
| Fracture | Irregular/Uneven |
| Chemical formula | FeS 2 |
| Specific gravity | 4.875 calculated, 4.887 measured |
What is Marcasite?
The mineral marcasite, sometimes called "white iron pyrite", is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures contain the disulfide S22− ion, having a short bonding distance between the sulfur atoms. The structures differ in how these di-anions are arranged around the Fe2+ cations. Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure.
How to identify Marcasite
- Lustre: Metallic.
- Hardness: Mohs 6–6.5 — about as hard as a steel knife.
- Streak: Dark-grey to black.
- Habit: Orthorhombic crystal system.
Marcasite in different forms
Stones often confused with Marcasite
Frequently asked questions
How hard is Marcasite?
Marcasite is Mohs 6–6.5 on the hardness scale.
What colour is Marcasite?
Marcasite is typically gold, gray, white, brown, yellow (Tin-white on fresh surface, pale bronze-yellow, darkening on exposure, iridescent tarnish).