sedimentary
Yellow Jasper
Silicon Dioxide (SiO2) with Goethite/Iron oxide inclusions
Hardness: 6.5-7 on Mohs scale; Color: Mustard yellow to deep ochre; Luster: Dull to vitreous (waxy when polished); Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Mustard yellow to deep ochre
- Luster
- Dull to vitreous (waxy when polished)
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Mustard yellow to deep ochre; Luster: Dull to vitreous (waxy when polished); Crystal Structure: Cryptocrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the deposition of silica-rich fluids in volcanic ash or sedimentary environments. The yellow color results from high concentrations of iron oxide or goethite. These can date back from millions to hundreds of millions of years depending on the stratigraphic deposit.
Uses & applications
Predominantly used as a gemstone for jewelry (cabochons, beads), decorative carvings, lapidary art, and as an ornamental stone in polished form. Historically used for making tools and weapons due to its conchoidal fracture.
Geological facts
Jasper is an opaque variety of chalcedony. In ancient times, yellow jasper was often associated with sun deities and was considered a protective stone for travelers. Unlike other chakcedonies, jasper is categorized by its high impurities (up to 20%), which account for its opacity.
Field identification & locations
Identify in the field by its opacity (it will not let light through even at thin edges) and its smooth, waxy feel when water-worn. Commonly found in riverbeds, desert pavements, and near volcanic regions worldwide, notably in India, Russia, and the USA (California and Oregon).
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