sedimentary

River Jasper (Chert/Chalcedony mix)

Silicon Dioxide (SiO2) with iron oxide and chlorite inclusions

Hardness: 6.5-7 (Mohs scale); Color: Variegated green, yellow, and tan; Luster: Waxy to dull (vitreous when polished); Crystal structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.5–2.9.

Hardness: 6
Color: Variegated green, yellow, and tan
Luster: Waxy to dull (vitreous when polished)

Identified April 3, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and silicification of microcrystalline quartz in sedimentary environments, often associated with volcanic ash or hydrothermal fluids. This specimen shows signs of mechanical weathering and rounding from river transport.

Uses & applications

Used primarily for lapidary work, cabochons, landscaping, and as a raw material for stone tools (historically). Popular among hobbyist rock collectors.

Geological facts

Jasper is an opaque variety of chalcedony. The green color is typically attributed to silicate minerals like chlorite, while the yellow-tan banding is due to hydrated iron oxides like goethite.

Field identification & locations

Identify in the field by its hardness (cannot be scratched by a steel knife) and waxy texture. It is commonly found in riverbeds, gravel pits, and coastal areas where older sedimentary layers have eroded.

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