sedimentary

Chert (Yellow Jasper variant)

Silicon Dioxide (SiO2) - Microcrystalline Quartz

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale. Color: Opaque mustard yellow due to iron oxide (goethite) inclusions. Luster: Dull to waxy. Crystal Structure: Trigonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.7.

Hardness: 6
Luster: Dull to waxy

Identified May 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation from silica-rich fluids in sedimentary basins. This specimen likely dates from the Cretaceous or older.

Uses & applications

Used historically for stone tools due to sharp edges; currently used for lapidary work, decorative landscaping, and as a gemstone for jewelry (beads, cabochons).

Geological facts

Yellow jasper is known as a stone of protection and was often used by ancient civilizations for amulets. It is basically a highly impure, opaque form of chalcedony.

Field identification & locations

Identify by its characteristic conchoidal (shell-like) fracture, extreme hardness (will scratch glass), and opaque yellow-brown cortex. Commonly found in riverbeds or as nodules within limestone/chalk.