Rock Identifier
Yellow Jasper (Chert) (Silicon Dioxide (SiO2) with Iron Oxide impurities) — mineral
mineral

Yellow Jasper (Chert)

Silicon Dioxide (SiO2) with Iron Oxide impurities

Hardness: 6.5-7 Mohs scale. Color: Mustard yellow, yellowish-brown, dark ochre. Luster: Vitreous to waxy/smooth. Crystal Structure: Microcrystalline/Cryptocrystalline trigonal. Cleavage: None (exhibits smooth conchoidal fracture). Specific Gravity: ~2.6-2.65.

Hardness
6
Color
Mustard yellow, yellowish-brown, dark ochre
Luster
Vitreous to waxy/smooth
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Physical properties

Hardness: 6.5-7 Mohs scale. Color: Mustard yellow, yellowish-brown, dark ochre. Luster: Vitreous to waxy/smooth. Crystal Structure: Microcrystalline/Cryptocrystalline trigonal. Cleavage: None (exhibits smooth conchoidal fracture). Specific Gravity: ~2.6-2.65.

Formation & geological history

Formed when silica-rich fluids precipitate within sedimentary rock cavities, fractures, or volcanic ash beds. The distinct yellow to brown color is caused by finely dispersed goethite or iron oxide minerals incorporated during crystallization.

Uses & applications

Popular for lapidary work, cabochon cutting, tumbled stones, wire wrapping, and decorative carvings. Historically used for knapping sharp tools and arrowhead points due to its smooth conchoidal fracture.

Geological facts

Jasper has been used by humans for millennia, revered as a protective stone in ancient cultures. Yellow jasper specifically gets its earthy golden hues from hydrated iron oxides like goethite.

Field identification & locations

Can be identified in the field by its opaque appearance, waxy surface sheen, conchoidal fracture edges, and high hardness (cannot be scratched by a steel knife). Commonly found in riverbeds, gravel bars, and desert environments worldwide.

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