Jasper

Physical Properties

Hardness: 6.5-7 (Mohs); Color: Reddish-brown, brownish-red; Luster: Vitreous to dull; Crystal structure: Trigonal (cryptocrystalline); Cleavage: None; Fracture: Conchoidal; Specific Gravity: 2.58-2.91

Formation & Geological History

Forms through the deposition of silica from water-saturated solutions in volcanic ash or sedimentary beds. The presence of iron oxides gives it the reddish-brown hue. It can form in various geological ages but is often associated with ancient volcanic and sedimentary environments.

Uses & Applications

Used primarily in lapidary arts for cabochons, beads, and carvings. Also used historically for making stone tools due to its conchoidal fracture, and sometimes in interior decoration or as landscaping stone.

Geological Facts

Jasper has been used as a gemstone since antiquity. In many cultures, red-hued jaspers were believed to provide protection and courage. It is an opaque variety of chalcedony.

Field Identification & Locations

Identify in the field by its hardness (scratches glass), lack of transparency (unlike agate), and smooth, shell-like conchoidal fracture when broken. Commonly found in areas with high silica content like riverbeds or volcanic outcrops.

Identified on: 5/3/2026

Mode: Standard