Last updated on: 7/2/2009 12:21:19 PM
A crystalline form of calcium carbonate that occurs in coral, shells, pearls, stalactites, and water deposits. Aragonite was named after the Aragon region in Spain where it was first discovered. Its orthorhombic system forms compact, acicular crystals that make it harder and heavier than calcite. When aragonite is formed by water deposition of calcium carbonate, the crystals often grow in radiating flowers. Aragonite mines are located in Europe, Bolivia, and the U.S. (New Mexico, Arizona). Aragonite was used in antiquity for beads and decorative items. It can be converted to calcite with heat (470 C) and changes slowly to calcite at room temperature.
Synonyms and Related Terms
calcium carbonate; nacre; shell white; coral; Aragonit (Deut., Pol.); aragonita (Esp.); aragonito (Esp.); aragonite (Fr., Port.); aragoniet (Ned.)
|3.5 - 4.0|
|mol. wt. = 100.09|
|1.530, 1.682, 1.686|
Orthorhombic crystal system with platy or fibrous, acicular crystals that are often twinned. Reacts with acids to evolve carbon dioxide. Fluorescent. Brittle. Aragonite is harder and denser than calcite.
Luster = vitreous to resinous. Transparent to translucent. Fracture = subconchoidal. Streak = white
Strongly birefringent showing interference colors. Straight extinction
Hazards and Safety
No significant hazards.
Mallinckrodt Baker: MSDS
° R. Gettens, E. West Fitzhugh, R.Feller, "Calcium Carbonate Whites", Artists Pigments, Vol. 2., A. Roy ed. Oxford University Press, Oxford, 1993.
° Mineralogy Database: Aragonite