Goethite
ID: 44
Goethite
Chemical Formula
Fe³⁺O(OH)
Hardness (Mohs)
5 - 5.5
Crystal System
Orthorhombic
Streak
Yellowish brown, orange-yellow, ocher-yellow
Luster
Adamantine, Silky, Metallic, Dull
Diaphaneity
Opaque
Color
Brownish black, yellow-brown, reddish brown
Crystal Habit / Mode of Occurrence
Often stalactitic, fibrous, botryoidal, reniform (kidney-shaped), or earthy; rarely prismatic crystals.
Density
4.27 - 4.29
Fun Facts
It's a common mineral in soils and is often responsible for the yellowish-brown to brownish-red colors in dirt, clay, and rust.