sedimentary

Chert (Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 Mohs; Color: Reddish-brown, tan, and cream; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown, tan, and cream
Luster: Dull to waxy

Identified July 3, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Reddish-brown, tan, and cream; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Gravity: 2.6-2.7

Formation & geological history

Formed from the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. The red coloration is due to iron oxide impurities (hematite).

Uses & applications

Historically used for stone tools due to conchoidal fracture; modernly used as decorative stones, landscaping, and lapidary work.

Geological facts

This specimen shows brecciated or vein-like patterns where silica-rich fluids filled cracks in the original rock. Chert is one of the most common materials used by early humans for arrowheads and knives.

Field identification & locations

Identify in the field by its hardness (will scratch glass) and smooth, sharp edges when broken. Commonly found in stream beds or eroded out of limestone/dolomite formations.