sedimentary

Jasper / Chert Pebble

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

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

Identified July 25, 2026More sedimentary →

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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.