sedimentary

Chert (Jasper/Flint variety)

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: Reddish-brown, tan, or peach/pink; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65

Hardness: 7 (Mohs scale)
Color: Reddish-brown, tan, or peach/pink
Luster: Waxy to dull

Identified April 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation in saltwater environments. They often form as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and weapons due to sharp edges; currently used for lapidary work, jewelry (beads/cabochons), and as a landscape stone.

Geological facts

Because it breaks with a conchoidal fracture, it was the primary material for arrowheads and spear points for thousands of years. This specific specimen appears to have flake scars, suggesting it could be a 'lithic flake' or 'debitage' from prehistoric tool making.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), waxy feel, and smooth, shell-like (conchoidal) curves where it is broken. Commonly found in riverbeds and limestone regions.

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