sedimentary
Yellow Chert (River Stone)
Microcrystalline Quartz (SiO2)
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
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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.
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