sedimentary

Yellow Chert (River Pebble)

Microcrystalline or Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Tan to yellow-brown; Luster: Waxy to dull; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Tan to yellow-brown
Luster: Waxy to dull

Identified July 19, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Tan to yellow-brown; Luster: Waxy to dull; Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed as chemical precipitates or as biochemical deposits on the ocean floor, often replacing carbonate materials. This specific specimen has been subsequentely weathered and rounded through fluvial (river) transport.

Uses & applications

Historically used for stone tools (arrowheads). Today used in landscaping, road construction, and as decorative river stones.

Geological facts

Chert is so hard it can create sparks when struck against steel. It is nearly identical in composition to flint, though usually lighter in color. The yellow hue is often due to trace iron oxide (limonite) inclusions.

Field identification & locations

Look for a smooth, waxy texture and conchoidal (shell-like) fractures where broken. It will easily scratch glass. Commonly found in riverbeds, gravel pits, and sedimentary outcrops.