mineral
Chalcedony (Agatized Coral / Rough Chalcedony Node)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale. Color: Tan, cream, white, with translucent patches. Luster: Waxy to dull. Crystal structure: Cryptocrystalline (Trigonal). Cleavage: None (Conchoidal fracture). Specific Gravity: 2.6-2.64.
- Hardness
- 6
- Color
- Tan, cream, white, with translucent patches
- Luster
- Waxy to dull
Identified More mineral →
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, cream, white, with translucent patches. Luster: Waxy to dull. Crystal structure: Cryptocrystalline (Trigonal). Cleavage: None (Conchoidal fracture). Specific Gravity: 2.6-2.64.
Formation & geological history
Formed from silica-rich groundwater filling cavities in limestone or replacing organic material (like coral) over millions of years; often associated with Tertiary period formations.
Uses & applications
Lapidary work (cabs and tumbling), jewelry making, aquarium decor, and popular as a collector's specimen.
Geological facts
This specimen appears to be anagatized coral or a similar botryoidal chalcedony node. Over time, the original calcium carbonate of the coral skeleton was replaced by silica. Some pieces contain beautiful geodes or 'druzy' quartz inside the vugs.
Field identification & locations
Identify by its 'waxy' texture when broken, high hardness (cannot be scratched by a steel knife), and translucent edges when held to a light source. Commonly found in Florida, Georgia, and riverbeds in the Southeast US.
