sedimentary

Chert (Jasper variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Reddish-brown, tan, and yellow due to iron oxide inclusions; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown, tan, and yellow due to iron oxide inclusions
Luster: Dull to waxy

Identified April 5, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms) or chemical precipitation from hydrothermal fluids in sedimentary environments. Common in ancient limestone or dolomite beds.

Uses & applications

Historically used for stone tools (arrowheads/scrapers) due to its sharp conchoidal fracture. Today used for lapidary work, landscaping, and as a collector specimen.

Geological facts

Jasper is an opaque variety of chalcedony. The reddish hues in this specimen are likely caused by impurities of hematite (iron oxide). It was one of the primary materials used by Paleolithic humans for tool-making.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and its conchoidal (shell-like) fracture edges. Commonly found in riverbeds or within sedimentary rock outcrops.