sedimentary
Jasper (Iron-stained Chert)
Silicon Dioxide (SiO2) with Iron Oxides
Hardness: 6.5-7 Mohs scale. Color: Ocher, brownish-yellow, and orange-red hues. Luster: Waxy to dull. Crystal structure: Microcrystalline/Cryptocrystalline quartz. Cleavage: None (conchoidal fracture). Specific gravity: 2.58-2.91.
- Hardness
- 6
- Color
- Ocher, brownish-yellow, and orange-red hues
- Luster
- Waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs scale. Color: Ocher, brownish-yellow, and orange-red hues. Luster: Waxy to dull. Crystal structure: Microcrystalline/Cryptocrystalline quartz. Cleavage: None (conchoidal fracture). Specific gravity: 2.58-2.91.
Formation & geological history
Formed as microcrystalline quartz deposits in sedimentary environments, often precipitated from silica-rich fluids in ocean beds, lakes, or groundwater, where iron oxide minerals (like goethite or limonite) impart yellow, orange, and brown coloration.
Uses & applications
Used for lapidary arts, tumbling, jewelry making (cabochons), landscape decoration, and rock collecting. Historically used by ancient cultures to fashion stone tools and arrowheads due to its sharp conchoidal fracture.
Geological facts
Yellow jasper gets its mustard-to-ocher color specifically from hydrated iron oxide minerals like goethite. Smooth river-worn pebbles like this specimen have been rounded by aquatic transport over thousands of years.
Field identification & locations
Identified in the field by its hardness (cannot be scratched by a steel pocketknife), smooth water-worn texture, waxy appearance, and rich yellowish-brown iron staining. Extremely common in river beds, gravel deposits, and beaches globally.
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