sedimentary
Chert (Yellow Jasper)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Mustard yellow, tan, orange, and brown. Luster: Waxy to dull. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Mustard yellow, tan, orange, and brown
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Mustard yellow, tan, orange, and brown. Luster: Waxy to dull. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through the accumulation of silica-rich fluids within sedimentary rock layers, often replacing limestone or organic matter. This specimen appears to be a stream-tumbled or weathered nodule.
Uses & applications
Historically used for stone tools (flintknapping) due to its sharp edges. Currently used in jewelry as semi-precious jasper, for decorative landscaping, and as a common lapidary material for tumbling.
Geological facts
Yellow jasper is often associated with iron oxide inclusions (limonite or goethite) which give it the characteristic yellow hue. It has been used by humans for thousands of years to create scrapers and arrowheads.
Field identification & locations
Identify in the field by its smooth, waxy feel and shell-like (conchoidal) fracture patterns when broken. Commonly found in riverbeds, gravel pits, and sedimentary basins worldwide. It will easily scratch glass.
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