Chert (Jasper/Chalcedony variety)

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: honey-yellow, orange-brown, and tan; Luster: waxy to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: none, exhibits conchoidal fracture; Specific gravity: 2.6-2.65

Formation & Geological History

Formed through the accumulation of silica-rich fluids in sedimentary basins or by the replacement of limestone. This specimen likely formed during the Cenozoic or Mesozoic eras through chemical precipitation.

Uses & Applications

Historically used for stone tools (knapping); currently used for lapidary work, jewelry (cabochons), and as a decorative landscaping rock.

Geological Facts

Because of its high hardness and conchoidal fracture, this material was one of the most important resources for prehistoric humans to create sharp-edged arrowheads and knives.

Field Identification & Locations

Identify by its 'waxy' appearance, hardness (it will scratch glass), and the shell-like (conchoidal) curves where it has chipped. Commonly found in riverbeds, desert pavements, and limestone outcrops.

Identified on: 5/1/2026

Mode: Standard