sedimentary

Yellow Chert

Chert (Cryptocrystalline Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale. Color: Mustard yellow, tan, or ochre. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Hardness: 6
Color: Mustard yellow, tan, or ochre
Luster: Waxy to dull

Identified July 16, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Mustard yellow, tan, or ochre. Luster: Waxy to dull. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolarians) or chemical precipitation from silica-rich fluids within limestone or chalk beds. Often Paleozoic or Mesozoic in age.

Uses & applications

Historically used for stone tools (knapping) due to its sharp edges. Currently used as road aggregate, in landscaping, and as lapidary material for tumbling.

Geological facts

Chert is so durable that it often remains in creek beds long after the surrounding limestone has eroded away. Yellow varieties are frequently colored by goethite or limonite inclusions.

Field identification & locations

Identify by its waxy texture, smooth conchoidal (shell-like) fractures, and the fact that it can scratch glass. Common in river gravels and sedimentary outcrops globally.