sedimentary
Yellow Jasper / Chert
Silicon Dioxide (SiO2) with Goethite or Limonite inclusions
Hardness: 6.5-7 on Mohs scale; Color: Yellow, mustard, or tan; Luster: Waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91
- Hardness
- 6
- Color
- Yellow, mustard, or tan
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Yellow, mustard, or tan; Luster: Waxy to dull; Crystal structure: Microcrystalline (trigonal); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91
Formation & geological history
Formed from the precipitation of silica-rich fluids in sedimentary environments or as primary chemical precipitates. Commonly associated with marine environments where silica settles on the ocean floor, often found in Paleozoic to Cenozoic formations.
Uses & applications
Used in the jewelry industry for cabochons and beads, as an ornamental stone for carvings, and occasionally in landscaping. Historically used for making sharp tools and arrowheads due to its conchoidal fracture.
Geological facts
Jasper is an opaque variety of chalcedony. The yellow coloration is specifically caused by the presence of iron oxide minerals like goethite. In ancient times, it was believed to be a stone of protection and endurance.
Field identification & locations
Identify in the field by its smooth, river-worn texture (if found in water), lack of visible grain, and waxy luster when freshly broken. It cannot be scratched by a steel knife. Common in riverbeds, glacial till, and coastal areas throughout North America and Brazil.
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