sedimentary
Chert with Quartz Veins
Microcrystalline silica (SiO2)
Hardness: 7 Mohs; Color: Brownish-grey with white veins; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 7 Mohs
- Color
- Brownish-grey with white veins
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 Mohs; Color: Brownish-grey with white veins; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Forms through the accumulation of silica-rich organic remains or chemical precipitation in marine or groundwater environments. Often found as nodules in limestone.
Uses & applications
Historically used for stone tools; currently used in construction aggregate and as decorative landscaping stones.
Geological facts
Chert is so hard it can strike sparks from steel. Ancient civilizations used it extensively for arrowheads and scrapers due to its sharp edges.
Field identification & locations
Identify by its hardness (scratches glass), waxy appearance, and smooth, curved fracture surfaces. Commonly found in riverbeds and sedimentary outcrops.
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