sedimentary
Chert (Jasper/Agate mix)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Brown, tan, and reddish-brown; Luster: Waxy to vitreous (glassy); Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Brown, tan, and reddish-brown
- Luster
- Waxy to vitreous (glassy)
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Brown, tan, and reddish-brown; Luster: Waxy to vitreous (glassy); Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Commonly formed from the accumulation of silica-rich organic remains (like diatoms) or chemical precipitation from fluids in sedimentary basins. Hardened over millions of years through lithification.
Uses & applications
Tumbled for jewelry, historical use for stone tools (flint knapping) due to sharp edges, and general landscaping or collecting.
Geological facts
Chert is extremely durable and chemically stable. Ancient civilizations used similar material to create arrowheads and scrapers because it breaks into sharp, predictable edges.
Field identification & locations
Identification includes its waxy texture and inability to be scratched by a steel nail. This specific specimen shows water-worn rounding, likely from a river or stream bed.
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