sedimentary
Chert (Yellow Jasper/Flint)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Yellowish-brown to tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Yellowish-brown to tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Yellowish-brown to tan; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed via the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. This water-worn specimen likely originated from sedimentary beds and was smoothed by river or glacial transport.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges; currently used for lapidary work, decorative landscaping, and as a collector's specimen.
Geological facts
Yellow chert is often referred to as 'Jasper' when opaque. It was a primary material for prehistoric hand axes and arrowheads because its conchoidal fracture creates edges sharper than a steel scalpel.
Field identification & locations
Identify in the field by its waxy texture and ability to scratch glass. Look for it in riverbeds or gravel pits. Use a rock hammer to check for the characteristic 'shell-like' curved fracture surfaces.
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