sedimentary

Chert

Microcrystalline Quartz (SiO2)

Hardness: 7 on Mohs scale; Color: Pale green and buff/tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 7 on Mohs scale
Color: Pale green and buff/tan
Luster: Waxy to dull

Identified June 26, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Pale green and buff/tan; Luster: Waxy to dull; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed by the precipitation of silica from groundwater or the accumulation of siliceous skeletal remains (like radiolarians) in marine environments. The specimen shows significant water-rounding, suggesting transport in a river or coastal environment. Found in the sedimentary sequences of the Appalachian orogen in Quebec.

Uses & applications

Historically used for stone tools (flintknapping); currently used as architectural aggregate, road surfacing, and as a semi-precious gemstone for tumbling and jewelry.

Geological facts

Chert is so hard it can strike sparks from steel. Because it breaks with sharp edges, it was one of the most important materials for early human technology, used to make arrowheads and scrapers.

Field identification & locations

Identified by its waxy luster, extreme hardness (scratches glass), and smooth, curved conchoidal fractures. Common in the Gaspé Peninsula and St. Lawrence region of Quebec due to the presence of Paleozoic sedimentary rock formations.