sedimentary

Chert / Jasper

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown to tan; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: Reddish-brown to tan
Luster: Dull to waxy

Identified March 16, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown to tan; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed from the accumulation of microcrystalline quartz. Often originates as siliceous ooze on the seafloor or through the replacement of limestone. Its age can range from Precambrian to Recent.

Uses & applications

Historically used for stone tools (arrowheads). Modernly used as a decorative gemstone, in jewelry (cabochons), and as an abrasive in industrial applications.

Geological facts

Jasper is an opaque variety of chalcedony. Many cultures throughout history attributed healing properties and strength to red jasper, often calling it the 'stone of endurance.'

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its smooth, shell-like fracture pattern, and its lack of visible grains. Common in sedimentary basins and as river-worn pebbles.