sedimentary
Chert (Jasper)
Silicon Dioxide (SiO2)
Hardness: 6.5–7 on Mohs scale. Color: Reddish-brown due to iron oxide impurities. Luster: Dull to waxy. Crystal Structure: Microcrystalline/Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.7.
- Hardness
- 6
- Color
- Reddish-brown due to iron oxide impurities
- Luster
- Dull to waxy
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: Reddish-brown due to iron oxide impurities. Luster: Dull to waxy. Crystal Structure: Microcrystalline/Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.7.
Formation & geological history
Formed through the accumulation of silica-rich microfossils (like radiolaria or diatoms) on the ocean floor, which later undergoes diagenesis, or through the chemical precipitation of silica-rich fluids. This specimen appears water-worn and tumbled.
Uses & applications
Historically used for stone tools (arrowheads/knives) due to its sharp conchoidal fracture. Modernly used in jewelry (as Jasper), lapidary arts, and as landscaping stone.
Geological facts
Jasper is a variety of chert that is opaque and usually colored red or yellow by iron inclusions. It has been used as a gemstone since antiquity and is mentioned in many ancient texts.
Field identification & locations
Identify in the field by its hardness (it can scratch glass), its smooth, waxy feel when wet, and its characteristic conchoidal fracture (shell-like curves). Common in riverbeds and glacial tills.
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