sedimentary

Chert (Yellow Jasper/Flint)

Microcrystalline quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Yellow-brown, tan, mustard; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Yellow-brown, tan, mustard
Luster: Waxy to dull

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Yellow-brown, tan, mustard; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation in sedimentary basins. It is often found as nodules or layers within limestone or shale. Most specimens date from the Phanerozoic eon.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used in landscaping, jewelry (as jasper), and as flint for spark-making. It has high value for lapidary tumbling.

Geological facts

Yellow chert is often referred to as 'Yellow Jasper' when it is opaque and high quality. It was a primary material for prehistoric humans due to its ability to break into sharp, glass-like edges.

Field identification & locations

Identify by its waxy texture and characteristic shell-like (conchoidal) fractures. It will easily scratch glass. Common in riverbeds and limestone outcrops worldwide.