sedimentary
Yellow Jasper / Chert
Silicon Dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5-7 (Mohs), Color: Yellow to tan with brown streaks, Luster: Waxy to vitreous, Crystal Structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs), Color: Yellow to tan with brown streaks, Luster: Waxy to vitreous, Crystal Structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the accumulation of silica-rich microfossils or precipitation from hydrothermal fluids in sedimentary environments. Its yellow color and banding are caused by oxidized iron (limonite or goethite) during its formation.
Uses & applications
Commonly used for lapidary work, cabochons for jewelry, pocket stones, decorative ornaments, and as a collector's specimen.
Geological facts
Jasper is an opaque variety of chalcedony. The name 'jasper' comes from the Greek word 'iaspis', meaning 'spotted stone'. It was highly prized in ancient civilizations like Mesopotamia and Egypt for seal stones and amulets.
Field identification & locations
Identify in the field by its smooth, waxy texture, opacity (does not transmit light like agate), and lack of visible grains. Commonly found in riverbeds, mountain ranges, and arid regions worldwide. It will scratch glass but cannot be scratched by a steel pocketknife.
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