Jasper (specifically Chert/Ironstone)

Physical Properties

Hardness: 6.5–7 (Mohs scale); Color: Rusty red, orange, and dark grey; Luster: Waxy to dull; Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.5–2.9

Formation & Geological History

Formed through the accumulation of silica-rich marine organisms or chemical precipitation of silica in sedimentary basins, often enriched by iron. This specimen shows oxidation typical of terrestrial weathering or iron-rich depositional environments.

Uses & Applications

Used primarily for lapidary work (cabochons, beads), decorative garden stones, and as a collectible geological specimen. Historically used for making sharp tools due to its conchoidal fracture.

Geological Facts

Jasper is an opaque variety of chalcedony. The red color in this specimen is caused by impurities of hematite or iron oxide. It has been used as a gemstone since antiquity and is mentioned in various historical texts.

Field Identification & Locations

Identify in the field by its smooth, shell-like (conchoidal) fracture surfaces and its ability to scratch glass. It is commonly found in riverbeds, desert pavements, and as nodules in limestone or volcanic rocks.

Identified on: 4/19/2026

Mode: Standard