sedimentary

Yellow Chert (River Stone)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 Mohs; Color: Tan, yellow, ochre; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Hardness: 7 Mohs
Color: Tan, yellow, ochre
Luster: Waxy to dull

Identified June 18, 2026More sedimentary →

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Physical properties

Hardness: 7 Mohs; Color: Tan, yellow, ochre; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments; this specific piece shows rounding from fluvial (river) transport and iron oxide staining.

Uses & applications

Used historically as a tool for flintknapping; modern uses include construction aggregate, landscaping, and lapidary for polished river stones.

Geological facts

Chert is so durable that it can survive millions of years of erosion, often ending up in riverbeds far from its original source. It was one of the primary materials used by prehistoric humans for arrowheads and scrapers.

Field identification & locations

Identify in the field by its waxy texture and conchoidal (shell-like) fracture patterns when broken; it will easily scratch glass. Commonly found in riverbeds, gravel pits, and sedimentary limestone formations.