sedimentary

Chert Pebble

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 Mohs scale. Color: Tan, brown, and grey. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.65.

Hardness: 6
Color: Tan, brown, and grey
Luster: Waxy to dull

Identified May 3, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs scale. Color: Tan, brown, and grey. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. Often found as nodules in limestone or as water-worn pebbles in riverbeds and beaches.

Uses & applications

Historically used for making stone tools (arrowheads). Modernly used in road construction, landscape gravel, and occasionally for lapidary work or as river stones.

Geological facts

This specimen is a water-worn, rounded pebble. Chert is essentially the same material as flint, though the name 'flint' is often reserved for dark specimens found in chalk. It is highly resistant to chemical weathering.

Field identification & locations

Identify by its hardness (it will scratch glass), its smooth waxy feel when polished, and the conchoidal (shell-like) chips visible on edges. Found worldwide in sedimentary basins.