Siderite
ID: 79
Siderite
Chemical Formula
FeCO₃
Hardness (Mohs)
3.75 - 4.25
Crystal System
Trigonal
Streak
White
Luster
Vitreous, may be silky to pearly
Diaphaneity
Transparent to Translucent
Color
Pale yellow to tan, gray, brown, green, red, black, and sometimes nearly colorless. Often becomes brownish upon weathering.
Crystal Habit / Mode of Occurrence
Typically rhombohedral crystals, often with curved faces, also tabular, botryoidal, massive, granular, and fibrous. Twinning is uncommon.
Fun Facts
Siderite is an important iron ore that lacks sulfur and phosphorus, making it valuable for iron production. Its name comes from the Greek word "sideros," meaning "iron."