mineral
Oco Geode
Silicon Dioxide (SiO2) with various inclusions
Hardness: 6.5-7 on Mohs scale; Color: Creamy white exterior with dark brown/translucent interior cavity; Luster: Waxy to vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Creamy white exterior with dark brown/translucent interior cavity; Luster: Waxy to vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed as gas bubbles trapped in volcanic lava flows, eventually filling with silica-rich water over millions of years. This specimen is an unbroken or tumbled whole geode (nodule).
Uses & applications
Used primarily for display, educational collections, metaphysical practices, and lapidary art like cabochons.
Geological facts
Oco geodes, also called 'Ocho' or 'Cloud' geodes, are famous for their feather-like patterns and druzy crystal centers. They are specifically sourced from the Rio Grande do Sul region of Brazil.
Field identification & locations
Identify by the smooth, rounded 'potato-like' exterior and a small natural cavity or 'window' revealing internal crystallization. Commonly found in basaltic rocks in Brazil.
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