Aragonite

Aragonite is a carbonate mineral, ane o the twa common, naiturally occurrin, crystal furms o calcium carbonate, CaCO₃ (the ither furm bein the mineral calcite). It is furmed bi biological an pheesical processes, includin precipitation frae marine an freshwatter environments.

Aragonite
Aragonite frae Salsignes Mine, Aude department, France Size: 30x30x20 cm
General
Category	Carbonate mineral
Formula (repeatin unit)	CaCO3
Strunz clessification	05.AB.15
Creestal seestem	Orthorhombic
Space group	Orthorhombic (2/m 2/m 2/m) - dipyramidal
Unit cell	a = 4.95 Å, b = 7.96 Å, c = 5.74 Å; Z = 4
Identification
Colour	White, reid, yellae, orange, green, purpie, grey, blae an broun
Creestal habit	Pseudohexagonal, prismatic crystals, acicular, columnar, globular, reniform, pisolitic, coralloidal, stalactitic, internally bandit
Twinnin	Polysynthetic parallel tae {100} cyclically on {110}
Cleavage	Distinct on {010}, imperfect {110} an {011}
Fractur	Subconchoidal
Tenacity	Brickle
Mohs scale haurdness	3.5-4
Skinkle	Vitreous, resinous on fracture surfaces
Streak	White
Diaphaneity	Leamin tae skyre
Speceefic gravity	2.95
Optical properties	Biaxial (-)
Refractive index	nα = 1.529 - 1.530 nβ = 1.680 - 1.682 nγ = 1.685 - 1.686
Birefringence	δ = 0.156
2V angle	18°
Solubility	Dilute acid
Ither chairacteristics	Fluorescence: fauch rose, yellae, white or blaeish; phosphorescence: greenish or white (LW UV); yellaeish (SW UV)
References	[1][2][3]

Aragonite's crystal lattice differs frae that o calcite, resultin in a different crystal shape, an orthorhombic seestem wi acicular crystals. Repeatit twinnin results in pseudo-hexagonal furms. Aragonite mey be columnar or fibrous, occasionally in branchin stalactitic furms cried flos-ferri ("flouers o airn") frae thair association wi the ores at the Carinthian airn mines.

References

1. Mindat.org
2. Handbook of Mineralogy
3. Webmineral data