sedimentary
Chert (Flint/Jasper variety)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, and translucent cream; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, and translucent cream
- Luster
- Waxy to vitreous
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, brown, and translucent cream; Luster: Waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7.
Formation & geological history
Formed by the precipitation of silica from groundwater or the accumulation of siliceous skeletal remains (like diatoms or radiolarians). It occurs as nodules or layered beds within carbonate rocks like limestone.
Uses & applications
Historically used for stone tools and weapons due to sharp edges; industrial use as decorative stone, road surfacing, and as a component in ceramics.
Geological facts
Because it breaks with a conchoidal fracture creating sharp edges, it was the primary material for prehistoric arrowheads and scrapers. It is chemically very resistant to weathering.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel blade), waxy texture, and the way it flakes off in smooth curves (conchoidal fracture). Common in river beds and sedimentary outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite
sedimentary