mineral
Brown Chalcedony (Agate/Jasper)
Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 Mohs; Color: Brown to reddish-brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None; Conchoidal fracture.
- Hardness
- 6
- Color
- Brown to reddish-brown
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown to reddish-brown; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microscopic); Cleavage: None; Conchoidal fracture.
Formation & geological history
Formed by the deposition of silica from groundwater in cavities of volcanic or sedimentary rocks. This specific specimen appears to be water-worn or weathered.
Uses & applications
Used primarily for lapidary work, jewelry (beads, cabochons), and as a decorative collector's stone.
Geological facts
Chalcedony is a broad term that includes agate, jasper, and carnelian. It has been used since the Bronze Age for seals and amulets because it does not stick to hot wax.
Field identification & locations
Identify by its waxy luster, smoothness, and the way it breaks along curved (conchoidal) surfaces. Commonly found in riverbeds, gravel pits, and desert washes.
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