sedimentary

Chert (containing Iron Oxide)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale); Color: White to tan with brown/orange iron staining; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 6
Color: White to tan with brown/orange iron staining
Luster: Waxy to dull

Identified April 10, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: White to tan with brown/orange iron staining; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.

Uses & applications

Historically used for stone tools and arrowheads; currently used in construction aggregate, road surfacing, and as a semi-precious stone for lapidary work.

Geological facts

Chert was one of the most important minerals for prehistoric humans because its conchoidal fracture produces extremely sharp edges, ideal for cutting tools.

Field identification & locations

Identify in the field by its hardness (scratches glass), waxy luster on fresh surfaces, and smooth, curved (conchoidal) fracture patterns. Frequently found in sedimentary basins.