Geology Home Page
Roger Weller, geology instructor
Chemical Group: carbonate
Chemical Formula: CaCO3
Color: white, gray, yellow, green, pink, red, violet
Streak: white Transparency: transparent to translucent
Hardness: 3.5 to 4
Specific Gravity: 2.93 to 2.95
Fracture: subconchoidal Luster: vitreous to resinous
Cleavage: two directions
Crystal Forms and habits:
Aragonite is commonly acicular (see cave formations).
Another common form is a pseudo-hexagonal plate produced by twinning.
Identifying Characteristics: Fizzes with hydrochloric like calcite
Occurrences: Bisbee, Arizona (acicular) and Ft. Collins, Colorado (hexagonal twins)
Toxicity: when-swallowed- low when inhaled- low
Additional Information: Aragonite is less stable than calcite and will often revert to calcite.