sedimentary

Yellow Chert (Gold-colored River Pebble)

Microcrystalline Quartz (SiO2) with Limonite/Goethite staining

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Dull yellow to mustard gold; Luster: Waxy to dull (earthy); Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Dull yellow to mustard gold
Luster: Waxy to dull (earthy)

Identified March 26, 2026More sedimentary →

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Physical properties

Hardness: 7 on Mohs scale; Color: Dull yellow to mustard gold; Luster: Waxy to dull (earthy); Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the precipitation of silica in sedimentary environments or by the replacement of carbonate rocks. This specimen is a 'river cobble,' rounded by water transport over millions of years, likely dating from the Paleozoic to Cenozoic eras.

Uses & applications

Used historically for stone tools and fire-starting (flint); currently used as architectural aggregate, landscaping stone, and occasionally for lapidary work (cabochons).

Geological facts

Yellow chert gets its distinctive color from iron oxide impurities (Limonite). It is one of the most durable rocks, often surviving long-distance river transport that destroys softer minerals.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), smooth rounded texture from water wear, and lack of visible grains. It is very common in riverbeds, glacial tills, and desert pavements worldwide.