sedimentary

Chert (Flint)

Chert (Cryptocrystalline Silica, SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Gray, tan, and brown with distinct banding; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.65

Hardness: 7 on Mohs scale
Color: Gray, tan, and brown with distinct banding
Luster: Waxy to dull

Identified July 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or through chemical precipitation in marine environments; often occurs as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools (knapping) and fire-starting; currently used in construction aggregate, road surfacing, and as a semi-precious stone for lapidary work.

Geological facts

Chert has a conchoidal fracture that produces very sharp edges, which made it the primary material for prehistoric arrowheads and spear points. Banded varieties like this one are sometimes referred to as 'striped flint'.

Field identification & locations

Identify by its hardness (scratches glass), waxy texture, and shell-like (conchoidal) curved break patterns. Commonly found in riverbeds or eroding out of sedimentary rock layers.