sedimentary

Chert (Commonly known as Jasper or Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, tan, and grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Yellow-brown, tan, and grey
Luster: Waxy to dull

Identified May 25, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, tan, and grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed via the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation of silica in marine or groundwater environments. It typically forms nodules in limestone or chalk beds.

Uses & applications

Historically used for making stone tools (arrowheads). Modern uses include construction aggregate, road surfacing, and as a semi-precious gemstone in jewelry when it displays attractive colors (Jasper).

Geological facts

Chert has been used by humans for over 2 million years because its conchoidal fracture produces extremely sharp edges. It is chemically identical to quartz but has a different internal structure.

Field identification & locations

Identify by its hardness (it will scratch glass), its waxy feel, and its shell-like (conchoidal) fracture pattern. Commonly found in riverbeds, glacial tills, and sedimentary rock outcrops.