Marcasite
ID: 48
Marcasite
Chemical Formula
FeS₂
Hardness (Mohs)
6 - 6.5
Crystal System
Orthorhombic
Streak
Dark-gray to black.
Luster
Metallic, Sub-Metallic
Diaphaneity
opaque
Color
Pale brass-yellow, tin-white on fresh exposures.
Density
4.887
Fun Facts
It's a polymorph of pyrite, meaning it has the same chemical formula (FeS2) but a different crystal structure, often forming in distinctive "cockscomb" or "radiating" habits.