Rock Identifier
Opalized Belemnite Fossil (Belemnitella (Opalized replacement)) — fossil
fossil

Opalized Belemnite Fossil

Belemnitella (Opalized replacement)

AI-generated identification · may be incorrect

Hardness 5.5-6.5 on Mohs scale, vitreous to sub-vitreous luster, amorphous crystal structure, exhibits a distinctive bullet-shaped guard with play-of-color.

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Physical properties

Hardness 5.5-6.5 on Mohs scale, vitreous to sub-vitreous luster, amorphous crystal structure, exhibits a distinctive bullet-shaped guard with play-of-color.

Formation & geological history

Formed when acidic silica-rich groundwater dissolved internal organic structures of Cretaceous squid-like cephalopods, precipitating precious opal in the void over millions of years.

Uses & applications

Highly prized by collectors and used as a unique, rare gemstone in high-end jewelry.

Geological facts

This specimen is a pseudomorph, where precious opal completely replaced the original calcite shell of an extinct marine mollusk.

Field identification & locations

Found almost exclusively in the opal fields of Coober Pedy and Lightning Ridge, Australia; identified by its unmistakable fossil guard shape combined with opalescence.

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