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Aragonite

Aragonite
All data from the card 23
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
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)

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'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.

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Text from Wikipedia, CC BY-SA 4.0 · Source article