sedimentary
Banded Chert (or River Jasper)
Microcrystalline Quartz (SiO2) with iron oxide impurities
Hardness: 6.5-7 (Mohs). Color: Tan, brown, white, and yellow banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7. Highly durable and smooth surface texture.
- Hardness
- 6
- Color
- Tan, brown, white, and yellow banding
- Luster
- Waxy to vitreous
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 6.5-7 (Mohs). Color: Tan, brown, white, and yellow banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microscopic). Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7. Highly durable and smooth surface texture.
Formation & geological history
Formed by the accumulation of silica-rich organic or chemical remains in deep-sea or shallow-water environments. Over millions of years, silica replaces other minerals or fills voids. Weathering and water transport in rivers often round these stones into smooth pebbles.
Uses & applications
Historically used for making stone tools (arrowheads/scrapers) due to sharp edges. Today used for landscaping, rock tumbling, lapidary cabochons, and as a collector's hobby item.
Geological facts
Chert is essentially the same mineral as flint, though 'flint' usually refers to dark nodules in chalk. Banded varieties are often called 'Jasper' by river rock collectors when they display vibrant colors. It is one of the most common rocks used by prehistoric humans.
Field identification & locations
Identified by its extreme hardness (will scratch glass), waxy feel, and smooth curves where it has broken (conchoidal fracture). Commonly found in riverbeds, gravel pits, and coastal eroded areas. Look for the distinct parallel banding patterns.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Sandstone
Arenite
sedimentary