sedimentary

Chert (variably called Jasper or Agate)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7.0 (Mohs). Color: Brown, tan, and dark gray bands. Luster: Waxy to vitreous. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Brown, tan, and dark gray bands
Luster: Waxy to vitreous

Identified June 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7.0 (Mohs). Color: Brown, tan, and dark gray bands. Luster: Waxy to vitreous. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.

Formation & geological history

Formed through the accumulation of silica-rich marine organisms or chemical precipitation from hydrothermal fluids in rock cavities. This specimen appears water-worn, likely from a river or beach deposit.

Uses & applications

Historically used for stone tools (arrowheads); currently used in lapidary work, jewelry, and as tumbled decorative stones.

Geological facts

Chert was one of the most important minerals for early humans because its conchoidal fracture creates extremely sharp edges; it is chemically identical to quartz but with a different internal structure.

Field identification & locations

Identify by its hardness (cannot be scratched by a steel nail) and its smooth, waxy surface. Commonly found in gravel beds, riverbanks, and limestone outcrops.