sedimentary

Chert (Jasper/Flint variety)

Microcrystalline Quartz (SiO2)

Hardness: 6.5–7 (Mohs scale); Color: Variegated brown, grey, and green with white quartz veins; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6–2.65.

Hardness: 6
Color: Variegated brown, grey, and green with white quartz veins
Luster: Waxy to dull

Identified March 22, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (like radiolarians or diatoms) or chemical precipitation from hydrothermal fluids in marine environments. This specimen shows secondary quartz veining where silica-rich water filled later-stage fractures.

Uses & applications

Historically used for stone tools due to its sharp conchoidal fracture. Modern uses include decorative landscaping, lapidary work (polishing for jewelry like cabochons), and road surfacing materials.

Geological facts

Chert is so durable that it often survives millions of years of erosion, frequently found as 'stream tumble' or beach pebbles. Specimens with distinct color banding are often colloquially referred to as Jasper.

Field identification & locations

Identify in the field by its hardness (it should scratch steel) and its smooth, shell-like (conchoidal) fracture pattern. It is commonly found in sedimentary basins, riverbeds, and glacial deposits worldwide. Collectors look for unique color swirls or patterns.

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