Aragonite Crystals

Aragonite crystals from Gran Canaria.
Chemical Formula: CaCO3
Color: colorless, white, gray, yellowish white, or reddish white.
Diaphaniety: Transparent to translucent
Hardness: 3.5-4 - Copper Penny-Flourite
Density: 2.93
Luster: Vitreous (Glassy)
Streak: white
Crystal System: Orthorhombic - Dipyramidal H-M Symbol (2/m 2/m 2/m) Space Group: Pmcn

Aragonite hedgehog, Ravenska Jama, Slovenia.
Aragonite, Lechuguilla, NM, U.S.A.. Public Domain.

Aragonite Crystals are calcium carbonate or limestone (CaCO3) in its mineral form. There are two possible forms of calcium carbonate, the other one is called Calcite.

Aragonite is named after Aragon in Spain, or more acurately after the village Molina de Aragón, where it was first described (locus typicus, type locale). But it is rater common and found worldwide. It is also common in caves, but it is much less common than calcite.

Aragonite has a different crystal system, which is caused by another spacial structure of the same Elements. It can be distinguished from calcite by its greater hardness and specific gravity. The crystal system depends on the chemical and physical conditions whilst the growth of the crystals. Higher temperatures, the presence of sulphur and biological activities are thought to be likely causes for the formation of aragonite instead of calcite.