sedimentary
Chert (Commonly known as Jasper or Flint)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, tan, and grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 6
- Color
- Yellow-brown, tan, and grey
- Luster
- Waxy to dull
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Yellow-brown, tan, and grey; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed via the accumulation of silica-rich microfossils (like radiolaria or diatoms) or chemical precipitation of silica in marine or groundwater environments. It typically forms nodules in limestone or chalk beds.
Uses & applications
Historically used for making stone tools (arrowheads). Modern uses include construction aggregate, road surfacing, and as a semi-precious gemstone in jewelry when it displays attractive colors (Jasper).
Geological facts
Chert has been used by humans for over 2 million years because its conchoidal fracture produces extremely sharp edges. It is chemically identical to quartz but has a different internal structure.
Field identification & locations
Identify by its hardness (it will scratch glass), its waxy feel, and its shell-like (conchoidal) fracture pattern. Commonly found in riverbeds, glacial tills, and sedimentary rock outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary