sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Mohs hardness: 6.5-7; Color: Olive green to brownish-green with iron oxide streaks; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
- Hardness
- 6
- Color
- Olive green to brownish-green with iron oxide streaks
- Luster
- Waxy to vitreous
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Mohs hardness: 6.5-7; Color: Olive green to brownish-green with iron oxide streaks; Luster: Waxy to vitreous; Crystal structure: Trigonal/Microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7.
Formation & geological history
Formed primarily by the accumulation of silica-rich organic remains (like radiolaria or diatoms) or by chemical precipitation in marine environments. This specimen shows signs of river or stream tumbling, giving it a smooth, rounded water-worn texture.
Uses & applications
Historically used for stone tools and weapons due to its sharp conchoidal fracture. Currently used in lapidary work, jewelry, landscaping, and as a decorative collector's item.
Geological facts
Chert is so durable that it often survives long after the rock matrix it formed in has eroded away. It is often found in riverbeds and on beaches worldwide.
Field identification & locations
Identify in the field by its hardness (cannot be scratched by a steel knife), smooth waxy feel, and characteristic shell-like (conchoidal) fractures where it has chipped. Common in limestone regions and gravel deposits.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary