Geology Home Page
Roger Weller, geology instructor
Chemical Group: carbonate
Chemical Formula: FeCO3
Color: ash-gray, yellowish gray, greenish gray, brown,
Streak: white Transparency: translucent to sub-translucent
Hardness: 3.5 to 4
Specific Gravity: 3.83 to 3.88
Fracture: uneven to sub-conchoidal
Luster: vitreous to pearly
Cleavage: rhombohedral cleavage, 3 directions
Crystal Forms and Habit:
Crystal shapes are primarily rhombohedrons.
Crystal surfaces might be curved similar to dolomite.
Commonly found in cleavable masses.
May also occur in botryoidal forms, or compact, or earthy.
Identifying Characteristics: May resemble some sphalerite, but unlike sphalerite, can be attacked
by concentrated hydrochloric acid.
Uses: iron ore
Occurrences: Roxbury, Connecticut
Toxicity: when-swallowed- moderate when inhaled- moderate