sedimentary
Jasper / Chert Pebble
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale; Color: reddish-brown to dark purple/brown; Luster: earthy to vitreous; Crystal structure: trigonal/microcrystalline; Cleavage: none (conchoidal fracture).
- Hardness
- 6
- Color
- reddish-brown to dark purple/brown
- Luster
- earthy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: reddish-brown to dark purple/brown; Luster: earthy to vitreous; Crystal structure: trigonal/microcrystalline; Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the accumulation and recrystallization of silica-rich fluids or radiolarian muds in sedimentary marine environments, heavily iron-stained giving its dark reddish-brown hue.
Uses & applications
Used primarily as decorative pebbles, in landscaping, tumbling for rock collections, and historically as raw material for flint knapping and tools.
Geological facts
Reddish-brown jaspers get their rich earthy color from iron oxide inclusions (hematite/goethite) micro-dispersed within the silica matrix.
Field identification & locations
Identified by its high hardness, conchoidal fracture pattern, smooth water-worn surface, and dull to waxy luster. Commonly found along riverbeds, gravel pits, and oceanic beaches worldwide.
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