Aragonite is a polymorph of calcite. In hand sample, it can be distinguished from calcite by its lack of rhombohedral cleavage and, in sufficiently translucent samples, its lack of double refraction.
Physical Properties |
|
| Chemical formula | CaCO3 |
| Class | Carbonate |
| Crystal system | Orthorhombic |
| Habit | Acicular Tabular Prismatic Fibrous Radiating splays Crusts Masses of different morphologies |
| Color | Colorless to white Pale yellow Gray White Brown Red Pink Purple Orange Blue Green |
| Hardness | 3.5 to 4 |
| Specific gravity | 2.94 |
| Cleavage | Good (010), poor {110} |
| Fracture | Subconchoidal |
| Luster | Vitreous |
| Transparency | Transparent to translucent |
| Streak | White |
Optical Properties |
|
| PPL | Colorless, but may exhibit pale pastels High relief |
| XPL | Extremely high birefringence colors may look pastel, washed out, or almost neon High reliefParallel extinction |
| δ | 0.155 |
| Twinning | Contact Cyclic May appear pseudohexagonal |
| Extinction | Parallel |
Special properties |
Reacts with HCl (fizzes) |
| after Perkins, 386 |
Aragonite in Hand Sample
Aragonite
Obverse of the above sample
Aragonite with right-angle twinning
Aragonite in Thin Section
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