sedimentary
Chert with Quartz Veining
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Dark grey to black with white quartz veins and some iron oxidation (orange/brown), Luster: Dull to waxy, Crystal structure: Cryptocrystalline, Fracture: Conchoidal to irregular
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale), Color: Dark grey to black with white quartz veins and some iron oxidation (orange/brown), Luster: Dull to waxy, Crystal structure: Cryptocrystalline, Fracture: Conchoidal to irregular
Formation & geological history
Formed by the accumulation of siliceous remains of marine organisms or via chemical precipitation from silica-rich fluids in sedimentary basins. The white veins are later-stage quartz filled fractures.
Uses & applications
Historically used for making stone tools due to its conchoidal fracture. Modern uses include abrasives and road surfacing material.
Geological facts
Chert is essentially a dense form of quartz. It was highly prized by indigenous cultures globally for crafting arrowheads, knives, and scrapers because it produces a very sharp edge.
Field identification & locations
Identify in the field by its high hardness (it will scratch glass) and smooth, shell-like fracture surfaces. Often found as nodules or lenses within limestone formations.
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
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary