Crystal & mineral guide
Aragonite
CaCO₃
Orthorhombic CaCO₃ polymorph — higher SG than calcite; biogenic in shells.
Identify Aragonite with RockScan Get on the App StoreAbout Aragonite
Aragonite is calcite's denser polymorph. Forms pseudohexagonal twins, speleothems, and is the mineral of many mollusk shells and pearls' nacre. Metastable — converts to calcite over geologic time. Distinguished by higher SG and different crystal system.
Aragonite belongs in a crystal identifier workflow because photo cues — color zoning, crystal habit, and surface luster — combine with measurable traits like Mohs 3.5–4 and specific gravity 2.95. Use RockScan’s camera to get a first-pass ID, then confirm with the checklist below.
Aragonite properties
| Mohs hardness | 3.5–4 |
|---|---|
| Crystal system | Orthorhombic |
| Luster | Vitreous |
| Color | White, brown, blue, green |
| Composition | Calcium carbonate (polymorph of calcite) |
| Formation | Marine precipitates, hot springs, caves; biogenic shells |
| Occurrence | Spain, Morocco, Italy, Bahamas ooids |
| Specific gravity | 2.95 |
| Cleavage | Distinct |
How to identify Aragonite
- SG ~2.95 (higher than calcite)
- Pseudohexagonal cyclic twins
- Acid fizz like calcite
Collector notes
- Pearl nacre is aragonitic
- Flos ferri is a coral-like aragonite habit
Value context: Aesthetic twin clusters and flos ferri for collectors.
Aragonite FAQ
How do you identify Aragonite?
Aragonite (CaCO₃) is typically recognized by white, brown, blue, green color, vitreous luster, Mohs hardness 3.5–4, and orthorhombic crystal system. RockScan can suggest Aragonite from a photo and surface these checks on the result card.
What is Aragonite made of?
Aragonite composition: Calcium carbonate (polymorph of calcite). It forms via marine precipitates, hot springs, caves; biogenic shells and is found in Spain, Morocco, Italy, Bahamas ooids.
Is Aragonite valuable?
Aesthetic twin clusters and flos ferri for collectors.
