sedimentary

Chert (Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 7 Mohs; Color: Reddish-brown, tan, and dark gray; Luster: Waxy to dull; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 7 Mohs
Color: Reddish-brown, tan, and dark gray
Luster: Waxy to dull

Identified June 10, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Reddish-brown, tan, and dark gray; Luster: Waxy to dull; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.

Formation & geological history

Formed via the accumulation of silica-rich organic remains or chemical precipitation in marine environments, often replacing original limestone or occurring as nodules. Can be hundreds of millions of years old.

Uses & applications

Historically used for stone tools (arrowheads). Modern uses include landscaping, lapidary work (jewelry and cabochons), and as a structural filler in construction.

Geological facts

Red chert is specifically known as Jasper and owes its color to iron inclusions. It was one of the first materials humans ever used for tool-making due to its sharp, glass-like edges when broken.

Field identification & locations

Identify by its conchoidal (curved) fracture pattern, waxy texture, and extreme hardness (it will scratch glass). Commonly found in sedimentary basins and riverbeds globally.