sedimentary

Chert

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Brown, tan, and gray with iron staining; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal.

Hardness: 7 Mohs
Color: Brown, tan, and gray with iron staining
Luster: Dull to waxy

Identified July 1, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Brown, tan, and gray with iron staining; Luster: Dull to waxy; Structure: Microcrystalline/Cryptocrystalline; Fracture: Conchoidal.

Formation & geological history

Formed primarily through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation from groundwater within sedimentary beds like limestone.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to its sharp edges; currently used for road surfacing and as a decorative stone in landscaping.

Geological facts

Because it breaks with a conchoidal fracture like glass, it was the primary material for prehistoric tool making. It is very chemically stable and resistant to weathering.

Field identification & locations

Identify by its hardness (it will scratch glass) and its smooth, shell-like fracture surfaces. Often found in nodules within limestone or as river gravel.