sedimentary

Jasper (Chert)

Silicon Dioxide (SiO2) with iron oxide inclusions

Hardness: 6.5-7 on Mohs scale. Color: Deep red, maroon, and tan. Luster: Vitreous to waxy. Structure: Microcrystalline/cryptocrystalline quartz. Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.91.

Hardness: 6
Color: Deep red, maroon, and tan
Luster: Vitreous to waxy

Identified July 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily from the deposition of silica from volcanic ash or hydrothermal fluids in sedimentary basins. The red coloration is due to the presence of hematite or other iron oxides during formation.

Uses & applications

Used extensively as a gemstone for cabochons, beads, and carvings. Also used in ornamental stone decor and historically as a material for stone tools due to its sharp conchoidal fracture.

Geological facts

Jasper is an opaque variety of chalcedony. It has been used by humans for thousands of years; the Minoans used it for seals, and it is mentioned in numerous ancient texts as a stone of protection and strength.

Field identification & locations

Identify in the field by its hardness (will scratch glass), opaque nature, and smooth, curved (conchoidal) fractures. It is commonly found in river beds, desert washes, and near volcanic regions globally.

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