sedimentary

Chert (Yellow Jasper/Flint pebble)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs); Color: Yellow, tan, and dark grey/black; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Hardness: 6
Color: Yellow, tan, and dark grey/black
Luster: Waxy to dull

Identified May 25, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Yellow, tan, and dark grey/black; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65

Formation & geological history

Formed via the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. These rounded pebbles often originate from ancient riverbeds or coastal deposits where they have been smoothed by water erosion.

Uses & applications

Historically used for stone tools (arrowheads). Modern uses include landscaping, tumbling for hobbyists, and industrial abrasives. High-quality specimens are used in lapidary work.

Geological facts

Chert and its varieties like Jasper are known for their conchoidal fracture, meaning they break with smooth, curved surfaces. This made them essential for prehistoric tool making.

Field identification & locations

Identify by its hardness (it will scratch glass) and waxy luster when wet or polished. Often found in river gravels and on beaches. Look for the smooth, rounded surface indicating water transport.