mineral
Chalcedony (Agate/Carnelian)
Cryptocrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 (Mohs); Color: Waxy brown-orange (carnelian-like); Luster: Vitreous to waxy; Crystal structure: Trigonal/Monoclinic; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6
- Hardness
- 6
- Color
- Waxy brown-orange (carnelian-like)
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Waxy brown-orange (carnelian-like); Luster: Vitreous to waxy; Crystal structure: Trigonal/Monoclinic; Cleavage: None/Conchoidal fracture; Specific gravity: 2.6
Formation & geological history
Formed via precipitation of silica-rich fluids in cavities or veins of volcanic or sedimentary rocks. The location 43.5°N, 6.5°E corresponds to the Estérel Massif region in France, famous for its Permian rhyolites and associated chalcedonies/agates.
Uses & applications
Used extensively in jewelry as gemstones (cabochons), oratory stones, and by mineral collectors. Historically used for making tools and seals.
Geological facts
The Estérel region in France is a renowned European locality for colorful cryptocrystalline quartz, often associated with ancient volcanic activity from approximately 250 million years ago.
Field identification & locations
Identify by its waxy luster, hardness (it will scratch glass), and translucency when held to a light source. Commonly found as nodules or vein fillings in the red rhyolite of the Estérel mountains.
