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.