mineral
Botryoidal Chalcedony (Geode fragment)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: White to translucent gray; Luster: Waxy to vitreous; Structure: Cryptocrystalline (hexagonal system); No cleavage; Specific gravity 2.6
- Hardness
- 6
- Color
- White to translucent gray
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: White to translucent gray; Luster: Waxy to vitreous; Structure: Cryptocrystalline (hexagonal system); No cleavage; Specific gravity 2.6
Formation & geological history
Formed by the precipitation of silica from groundwater in cavities of volcanic or sedimentary rocks. The 'bubbly' botryoidal texture occurs as mineral layers grow outward from multiple centers.
Uses & applications
Used primarily as collector specimens, lapidary material for cabochons or beads, and in ornamental carvings.
Geological facts
The term 'botryoidal' is derived from the Greek word 'botrys', meaning a bunch of grapes. Chalcedony is the cryptocrystalline form of quartz.
Field identification & locations
Identify by its characteristic grape-like spherical clusters and extreme hardness (cannot be scratched by a steel knife). Commonly found in desert regions or volcanic basalt flows.
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