sedimentary
Chert (specifically a weathered Chert nodule or fragment)
Chert; Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 6.5-7 on the Mohs scale; Color: Cream, tan, or white; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Cream, tan, or white
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on the Mohs scale; Color: Cream, tan, or white; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation in marine environments. This specimen shows significant rounding and weathering, likely from water transport.
Uses & applications
Historically used for stone tools (flintknapping); currently used as a component in road construction, concrete aggregate, and decorative landscaping rock.
Geological facts
Chert is so hard it can scratch glass and steel. It was the primary material for arrowheads and spear tips for thousands of years because it breaks with razor-sharp edges.
Field identification & locations
Identify in the field by its hardness (it cannot be scratched by a steel knife) and its smooth, waxy texture. It often occurs as nodules within limestone or as river pebbles. Found globally in sedimentary basins.
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