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Aragonite (Photo) [abbr. Arg ]

Year of discovery: 1797 (Tarnowskie Góry, Poland, and Gallo river, Spain), 1893 (Japan)

Locality list: 304 localities of aragonite

• CaCO₃
• [Ca²⁺][CO₃]^2-

• Class: Aragonite group
• Class: Carbonate
• Soluble in: HCl (with bubbles), HNO₃ (with bubbles), H₂SO₄ (with bubbles)
• Fluorescence UV excitation (Yellow-Green), Phosphorescence, Thermoluminescence
• Phase transition: Transit to Calcite above 400 degree.
• Phase transition: Formed on transition of heated Vateirte above 440 degree or in boiling water.
• Substitution pseudomorph: Replaced by Dolomite.
• Formed at temperatures greater than 50 degree under ambient pressure and acidic condition. Calcite is formed at temperatures lower than 50 degree under ambient pressure and acidic condition
• Formed at any temperature under ambient pressure and alkaline condition.

• Polymorph: Calcite (Trigonal), Vaterite (Hexagonal)

• Ca => Mn: Rhodochrosite
• Ca => Mg: Magnesite
• Ca => Fe: Siderite
• Ca => Cd: Otavite
• Ca => Zn: Smithsonite
• Ca => Ni: Gaspéite (Gaspeite)
• Ca => Co: Spherocobaltite
• Ca => Ba: Witherite
• Ca => Sr: Strontianite
• Ca => Pb: Cerussite
• Ca => Na₂: Gregoryite

• Ca₂ => CaBa: Barytocalcite, Alstonite, Paralstonite
• Ca₂ => CaMn: Kutnohorite
• Ca₂ => CaFe: Ankerite

• [] => 6H₂O: Ikaite
• [] => H₂O: Monohydrocalcite

• Color: Colorless-White
• Streak: White
• Luster: Vitreous
• Diaphaneity: Transparent-Translucent

• Habit: Fibrous, Prismatic
• Aggregate: Dendritic, Amygdalodial
• Twin: Intrusion twin forms pseutohexagonal prismatic crystal

• Cleavage: Perfect on {010} (1 plane), Indistinct on {110} and {011} (4 planes)
• Hardness: 3.5-4
• Density: 2.9

• System: Orthorhombic
• Group: mmm, Pmcn
• Lattice: a=5.0, b=8.0, c=5.7

Etymology: Aragon district, Spain