sedimentary
Chert (Yellow variety)
Microcrystalline quartz (SiO2)
Hardness: 6.5-7 (Mohs); Color: Tan/yellowish-brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6
- Hardness
- 6
- Color
- Tan/yellowish-brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Tan/yellowish-brown; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments; often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for stone tools and arrowheads due to sharp edges; currently used as construction aggregate, road base, and occasionally for lapidary tumbling.
Geological facts
Chert is nearly identical to flint, but 'flint' is usually reserved for dark varieties found in chalk. This specimen shows the characteristic waxy luster and sharp, splintery edges common in chert nodules.
Field identification & locations
Look for a smooth, waxy texture and shell-like (conchoidal) fractures. It will easily scratch glass. Commonly found in riverbeds or eroded out of sedimentary outcrops.
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