mineral

Aragonite Star Cluster

Aragonite (CaCO3)

Hardness: 3.5-4 on Mohs scale; Color: Reddish-brown, orange, white; Luster: Vitreous to resinous; Crystal structure: Orthorhombic (often forming pseudo-hexagonal twinned prisms); Cleavage: Distinct in one direction.

Hardness: 3
Color: Reddish-brown, orange, white
Luster: Vitreous to resinous

Identified July 15, 2026More mineral →

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Physical properties

Formation & geological history

Formed at low temperatures near the Earth's surface in oxidized zones of ore deposits, hot springs, or sedimentary environments. These specific 'sputnik' clusters typically form in clay-rich soils via twinning.

Uses & applications

Primarily used as decorative display specimens for collectors and in metaphysical practices. Scientifically important for understanding ocean acidification effects on calcifying organisms.

Geological facts

Aragonite is a polymorph of Calcite, meaning they share the same chemical formula but different crystal systems. Over geological time, aragonite often reverts to the more stable calcite structure.

Field identification & locations

Identify by its distinctive twinned hexagonal prisms radiating from a central point. Most 'star' specimens come from the Molina de Arag3n region in Spain or regions in Morocco. It will effervesce (fizz) in contact with dilute hydrochloric acid.