sedimentary

Chert (Jasper transition)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 (Mohs); Color: Brown, tan, and yellow-ochre; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.7

Hardness: 6
Color: Brown, tan, and yellow-ochre
Luster: Dull to waxy

Identified April 11, 2026More sedimentary →

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Physical properties

Hardness: 6.5–7 (Mohs); Color: Brown, tan, and yellow-ochre; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.7

Formation & geological history

Formed from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments. This specimen shows significant rounding from fluvial (river) or glacial transport.

Uses & applications

Historically used for stone tools (knapping); modernly used for landscaping, as a gemstone (when colorful), and in construction aggregate.

Geological facts

Chert is so durable that it often survives millions of years of erosion that destroy other rocks. This specific specimen has a 'river-worn' or 'cobble' texture, indicating it was moved by water for a long period.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its smooth waxy feel when wet, and its characteristic curved (conchoidal) breaks. It is ubiquitous in river beds and gravel pits globally.