sedimentary
Chert (variously known as Flint or Jasper)
Microcrystalline or Cryptocrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale. Color: Tan, beige, light brown, white. Luster: Dull to waxy. Crystal Structure: Trigonal (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, light brown, white
- Luster
- Dull to waxy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale. Color: Tan, beige, light brown, white. Luster: Dull to waxy. Crystal Structure: Trigonal (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
Formation & geological history
Formed by the precipitation of silica from seawater or groundwater. Commonly occurs as nodules in limestone or chalk beds. Often associated with Precambrian to Holocene geological ages.
Uses & applications
Historically used for stone tools and weapons due to sharp fracture edges. Today used in construction aggregate, road surfacing, and as a decorative stone in landscaping.
Geological facts
Chert was one of the most important minerals for early humans because its conchoidal fracture creates edges sharper than a steel scalpel. Native Americans used it extensively for arrowheads.
Field identification & locations
Identify in the field by its hardness (it scrapes steel and glass) and the characteristic curved, shell-like (conchoidal) fracture pattern when broken. It is extremely common globally in sedimentary outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
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
Sandstone
Arenite
sedimentary