sedimentary
Chert (Jasper)
Silicon dioxide (SiO2) with impurities
Hardness: 6.5-7 (Mohs); Color: Mottled red, yellow, and tan; Luster: Waxy to dull; Crystal structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Mottled red, yellow, and tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Mottled red, yellow, and tan; Luster: Waxy to dull; Crystal structure: Microcrystalline quartz; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich fluids within sedimentary environments or replacing other minerals. This water-worn specimen likely originated in a riverbed or glacial deposit.
Uses & applications
Primarily used for lapidary work, jewelry (beads/cabochons), and as landscaping stone. Historically used for making sharp tools and arrowheads.
Geological facts
This specimen is a river-rounded pebble showing classic jasper coloration caused by varying levels of iron oxide (hematite for red, goethite for yellow).
Field identification & locations
Identify in the field by its smooth, waxy texture and inability to be scratched by a steel knife. It often features colorful mottling or banding. Commonly found in gravel pits and along stream banks.
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