sedimentary

Chert (Green variety)

Microcrystalline or cryptocrystalline Quartz (SiO2)

Hardness: 7 (Mohs scale); Color: Pale green to olive green with some iron staining; Luster: Waxy to dull; Crystal structure: Trigonal (microscopic); Cleavage: None, exhibits conchoidal (shell-like) fracture; Specific Gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Pale green to olive green with some iron staining
Luster: Waxy to dull

Identified April 6, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or by chemical precipitation from brine. This specific piece appears to be a nodule or layer formed in a sedimentary environment where trace minerals like chlorite or iron provided the green tint.

Uses & applications

Historically used for stone tools (arrowheads, scrapers) due to its sharp edges. Today used as an abrasive, in road construction (aggregate), and by lapidary hobbyists for polishing or tumbling.

Geological facts

Chert is so hard it will spark when struck against steel. Flint is a well-known variety of chert. Because of its hardness and resistance to erosion, it often persists in riverbeds long after surrounding limestone has dissolved.

Field identification & locations

Identify in the field by its hardness (it will scratch glass and steel), waxy feel, and common shell-shaped (conchoidal) breaks. It is ubiquitous in sedimentary basins globally.

Other sedimentary specimens

See all

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