sedimentary
Chert (specifically Yellow/Common Opal or Jasper mixture)
Silicon Dioxide (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Opaque yellow to tan with waxy luster. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
- Hardness
- 6
- Color
- Opaque yellow to tan with waxy luster
Identified More sedimentary →
Explore Chert (specifically Yellow/Common Opal or Jasper mixture) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Opaque yellow to tan with waxy luster. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
Formation & geological history
Formed through the accumulation of silica-rich microfossils on ancient seafloors or by inorganic precipitation from silica-saturated fluids in limestone or volcanic cavities.
Uses & applications
Historically used for stone tools (arrowheads). Modern uses include lapidary work, decorative landscaping, and as a raw material for silicon-based products.
Geological facts
Chert is remarkably durable and resistant to weathering. It was one of the first materials used by early humans to create sparking tools for fire and sharp edges for survival.
Field identification & locations
Identify in the field by its smooth, waxy surface and its tendency to break into sharp, curved edges like glass. Often found in stream beds or within limestone outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary