sedimentary
Yellow Jasper (Iron-stained Quartzite/Chert)
Silicon Dioxide (SiO2) with Hydrated Iron Oxide (Goehite/Limonite) inclusions
Hardness: 6.5-7 on Mohs scale; Color: Mustard yellow, tan, or golden-brown; Luster: Dull to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Mustard yellow, tan, or golden-brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Mustard yellow, tan, or golden-brown; Luster: Dull to waxy; Crystal Structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the process of silicification, where silica-rich fluids permeate sedimentary layers or volcanic ash over millions of years. The yellow hue is derived from iron impurities during the maturation of the silica gel into rock.
Uses & applications
Commonly used for lapidary work (cabochons and beads), ornamental carvings, and as a popular pocket stone for collectors. Historically used for making tools due to its durability and sharp fracture pattern.
Geological facts
Jasper is an opaque variety of chalcedony. In ancient times, yellow jasper was often referred to as a 'stone of protection' for travelers. High-quality pieces that exhibit scenic patterns are often called 'Picture Jasper'.
Field identification & locations
Identify in the field by its opacity (it will not let light through, unlike agate), its extreme hardness (cannot be scratched by a steel knife), and its smooth, water-worn texture if found in riverbeds. Common in arid regions of the Western USA, Madagascar, and Brazil.
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