sedimentary
Chert (White Chert or Flint)
Microcrystalline or cryptocrystalline quartz (SiO2)
Hardness: 7 on Mohs scale; Color: White to light gray; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- White to light gray
- 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: White to light gray; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from groundwater within limestone or chalk beds. It can date from the Precambrian to Holocene.
Uses & applications
Historically used for stone tools (knapping) and fire-starting. Currently used as road surfacing, concrete aggregate, and sometimes as a minor gemstone for lapidary work.
Geological facts
Because of its extreme hardness and conchoidal fracture, it produces edges sharper than a steel scalpel. Native Americans and other ancient cultures used white chert extensively for arrowheads and scrapers.
Field identification & locations
Identify in the field by its waxy appearance, extreme hardness (it will scratch glass and steel), and curved, shell-like (conchoidal) fracture patterns. Frequently found in riverbeds or eroding out of limestone outcrops.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary