sedimentary

Chert or chalcedony fragment (possibly agate)

Microcrystalline quartz, SiO₂

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; pale honey-beige, translucent edges, waxy to dull luster, and conchoidal fracture. Crystal grains are microscopic, so cleavage is absent; specific gravity is about 2.6.

Identified August 8, 2026More sedimentary →

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Physical properties

Hardness 6.5–7 Mohs; pale honey-beige, translucent edges, waxy to dull luster, and conchoidal fracture. Crystal grains are microscopic, so cleavage is absent; specific gravity is about 2.6.

Formation & geological history

Forms when silica-rich groundwater precipitates in cavities or replaces sediment, commonly during diagenesis. The small fragment cannot establish a precise age; chert and chalcedony occur from Precambrian rocks through recent deposits.

Uses & applications

Used for knappable tools, aggregate, decorative stone, and occasional cabochons or beads when translucent and patterned. This small, unpatterned fragment has minimal commercial value.

Geological facts

Its sharp curved fracture surfaces and glassy translucence distinguish quartz-based material from most ordinary limestone. Iron-oxide staining commonly produces the tan or honey coloration.

Field identification & locations

Common in sedimentary beds, gravel, weathered volcanic areas, and hydrothermal veins worldwide; notable sources include the Flint Hills, Texas, Oregon, and many agate localities. A steel file should not scratch it, though a fresh surface and hardness test are more reliable than appearance alone.