sedimentary

Likely waterworn jasper or chert pebble

Microcrystalline quartz (chalcedony), SiO₂

AI-generated identification · may be incorrect

Opaque, mottled brown, reddish, and gray; smooth, rounded surface with a dull-to-waxy luster. Quartz hardness is 7 Mohs; crystal structure is trigonal, though crystals are too fine to see, and cleavage is absent. Specific gravity is about 2.6.

Identified October 15, 2026More sedimentary →

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Physical properties

Formation & geological history

Silica-rich sediment or rock formed the microcrystalline quartz; iron compounds commonly create the coloration. The pebble’s rounded shape suggests transport and abrasion by water, but its age and exact origin cannot be determined from the image.

Uses & applications

Jasper and chert are used for ornaments, carvings, beads, and lapidary work; chert has also served as a toolstone.

Geological facts

Jasper is an opaque variety of chalcedony, while chert is a closely related fine-grained quartz rock; visual appearance alone may not distinguish them reliably.

Field identification & locations

Look for hardness, a waxy surface, and conchoidal fracture on a fresh break; this rounded specimen has no diagnostic features visible to pinpoint a locality. Common in silica-rich formations and stream gravels worldwide.