Yellow Jasper / Chert

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Yellow-brown, mustard, ochre; Luster: Waxy to dull; Crystal structure: Trigonal (Microcrystalline); Cleavage: None (Conchoidal fracture); Specific gravity: 2.58-2.91

Formation & Geological History

Formed from the deposition of silica in sedimentary environments or through the replacement of organic materials. The yellow color is typically due to the inclusion of iron oxides (Goethite). Geological age varies widely from Precambrian to Cenozoic.

Uses & Applications

Used in gemstone carvings, jewelry (cabochons), or as decoration. Historically used for making tools due to its sharp conchoidal fracture.

Geological Facts

Jasper is an opaque variety of chalcedony. Yellow jasper is often called 'Yellow King Jasper' and was historically used as a protective stone by travelers during the Middle Ages.

Field Identification & Locations

Identify in the field by its hardness (cannot be scratched by a steel knife), smooth waxy feel when polished by water, and shell-like fracture pattern. Commonly found in riverbeds, beaches, and desert environments worldwide.

Identified on: 4/17/2026

Mode: Standard