sedimentary

Chert (Pebble)

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale. Color: Grayish-brown with lighter quartz/calcite veins. Luster: Dull to waxy. Structure: Microcrystalline, non-porous with smooth rounded surfaces from water erosion.

Hardness: 7 on Mohs scale
Color: Grayish-brown with lighter quartz/calcite veins
Luster: Dull to waxy

Identified July 22, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale. Color: Grayish-brown with lighter quartz/calcite veins. Luster: Dull to waxy. Structure: Microcrystalline, non-porous with smooth rounded surfaces from water erosion.

Formation & geological history

Formed in marine or freshwater sedimentary environments through the deposition of silica-rich fluids or precipitation of siliceous ooze, later rounded and smoothed by stream or beach action.

Uses & applications

Historically used for stone tools and flintknapping; commonly used as gravel, river rock landscaping, and aggregate in construction.

Geological facts

Chert is extremely durable due to its high quartz content, often surviving erosion that wears away softer surrounding rocks. Varieties of chert include flint, jasper, and agate.

Field identification & locations

Can be identified by its conchoidal fracture (smooth curved shell-like breaks), hardness (scratches glass easily), smooth river-worn texture, and presence of fine quartz veinlets.