Aragonite Star Cluster
Aragonite · Mineral Specimen / Decorative Stone
Crystal System
Orthorhombic; typically forms pseudo-hexagonal twinned prisms creating a 'starburst' or 'sputnik' habit.
Mineral Group
Carbonates (Aragonite Group)
Chemical Formula
CaCO3 (Calcium Carbonate)
Formation Process
Commonly formed through low-temperature hydrothermal processes or as a secondary mineral in the oxidized zones of carbonate-rich environments.
About This Crystal
Reddish-brown to honey-orange cluster of radiating pseudo-hexagonal prisms. Translucent to opaque with a vitreous to resinous luster and distinct cyclic twinning.
Physical Characteristics
Color is reddish-brown; white streak; distinct cleavage on one plane; conchoidal fracture; 2.95 specific gravity; strong reaction to dilute HCl; often fluoresces yellow/cream under UV.
Optical Properties
Biaxial negative; Refractive Index of 1.530–1.685; high birefringence (0.155); no significant pleochroism in these massive clusters.
Hardness & Durability
Origin Region
Notable sources include Morocco (Tazouta), Spain (Aragon region), Mexico, and the USA. Found in the oxidized zones of ore deposits and hot springs.
Hardness & Durability
Mohs hardness 3.5 to 4.0; brittle tenacity; low durability for jewelry; susceptible to acids and scratches.
Care & Maintenance
Clean only with a soft, dry cloth or lukewarm soapy water; avoid ultrasonic/steam cleaners and all acids; store separately to prevent scratching.
Rarity & Value
Common as mineral specimens; price is generally low to moderate ($5-$50 depending on size/perfection); usually untreated but may be dyed in some commercial markets.
Special Characteristics
Displays cyclic twinning which creates the appearance of hexagonal symmetry despite its orthorhombic internal structure.
Lore & History
Named after the Aragon region of Spain in 1797; historically used in carvings; traditionally associated with grounding, 'earth healing,' and stabilizing energy in metaphysical practices.