sedimentary
Chert (vuggy/nodular)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale); Color: Cream, tan, white, and grayish; Luster: Waxy to dull (earthy in weathered areas); Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Cream, tan, white, and grayish
- Luster
- Waxy to dull (earthy in weathered areas)
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 (Mohs scale); Color: Cream, tan, white, and grayish; Luster: Waxy to dull (earthy in weathered areas); Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65.
Formation & geological history
Formed through the precipitation of silica-rich fluids in sedimentary rock cavities or by the replacement of calcium carbonate in limestone. These specimens common date from the Paleozoic to Mesozoic eras.
Uses & applications
Used historically for tool-making (arrowheads, scrapers) due to sharp edges; currently used for decorative stone, road ballast, and as a collector specimen.
Geological facts
This specimen contains a vug (cavity) often referred to as a 'rattle stone' if the inner nodule is loose. Chert is extremely chemically stable and can survive millions of years of weathering.
Field identification & locations
Identify in the field by its hardness (it should scratch glass), waxy texture when freshly broken, and conchoidal (shell-like) fracture. Commonly found in riverbeds and eroded 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