sedimentary

Chert (Flint)

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Creamy white to light tan; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Creamy white to light tan
Luster: Waxy to dull

Identified June 23, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Creamy white to light tan; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed primarily through the chemical precipitation of silica-rich fluids within sedimentary rock layers, often as nodules in limestone or chalk during the Phanerozoic eon.

Uses & applications

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

Geological facts

Small flakes or 'debitage' like this one are often evidence of ancient tool-making (lithic reduction). Because it breaks with a conchoidal fracture, it creates edges sharper than a surgeon's scalpel.

Field identification & locations

Identified in the field by its waxy texture, extreme hardness (scratches glass), and shell-like (conchoidal) fracture patterns. Frequently found in stream beds or limestone outcrops.