Aragonite is a naturally occuring crystal form of calcium carbonate and is a preciptate from salt and freshwater conditions. One form of aragonite occurs naturally in most mollusks. Crystallizing from calcium carbonate into orthorhombic translucent microscopic platelets and cemented by conchiolin, aragonite forms the nacre of most of the gems we refer to as pearls. This includes both natural and cultured pearls as well as the mother-of-pearl lining of hard shelled mollusks.

Aragonite is also found in crystal form, usually white, yellow, brown, green, blue, red, violet or colorless.

Gemological information

Gemological Information for Aragonite
Color Transparent to Opaque, Colorless and most other colors in light tones
Crystal Structure Orthorhombic
Refractive Index 1.53 to 1.685
Durability Fair to Poor
Hardness 3.5 - 4
Similar Stones Calcite
Treatments None Known
Country of Origin U.S., England, Italy, Spain, Austria, Bolivia, Czech Republic
Aragonite Care
Ultrasonic Cleaning Never
Steam Cleaning Never
Warm Soapy Water Usually Safe, Avoid Acids
Chemical Attack Attacked and Effervesces to Certain Acids
Light Sensitivity Natural Colors Stable
Heat Sensitivity Decrepitates at Higher Temps Converting to Calcite


  • Gem Reference Guide, Los Angeles: Gemological Institute of America, 1988. Pp. 15-16.
  • Schumann, Walter. Gemstones of the World, New York: Sterling Publishing, Co., 1977. Pp. 210.