mineral
Chalcedony (Agate/Carnelian)
Cryptocrystalline Quartz (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: translucent yellowish-orange to tan; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.64.
- Hardness
- 6
- Color
- translucent yellowish-orange to tan
- Luster
- waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: translucent yellowish-orange to tan; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific gravity: 2.6-2.64.
Formation & geological history
Formed via the deposition of silica from groundwater in cavities of volcanic and sedimentary rocks. Common in basaltic vugs.
Uses & applications
Used in jewelry, lapidary carvings, as semiprecious gemstones, and historically for artisanal tools and seals.
Geological facts
The name Chalcedony comes from the ancient Greek town Chalcedon. It has been used for beads and cylinder seals since the Bronze Age in Mesopotamia.
Field identification & locations
Identified by its waxy luster, translucency, and lack of visible crystals. Commonly found in riverbeds, beaches, and desert pavements as water-worn pebbles.
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