sedimentary
Brown Jasper / River Siltstone
Silicon Dioxide (SiO2) with iron oxide impurities
Hardness: 6.5-7 (Mohs); Color: Dark brown to mottled yellowish-brown; Luster: Dull to waxy; Structure: Microcrystalline quartz; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 6
- Color
- Dark brown to mottled yellowish-brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Dark brown to mottled yellowish-brown; Luster: Dull to waxy; Structure: Microcrystalline quartz; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the process of silicification within sedimentary layers or as water-worn river pebbles. Common in Mesozoic or Cenozoic deposits across riverbeds and ancient alluvial plains.
Uses & applications
Mainly used as a decorative stone, lapidary material for cabochons, or as garden landscaping stones.
Geological facts
The brown coloration is typically caused by goethite or limonite (iron oxides) trapped within the quartz matrix. Jasper has been used since ancient times for cylinder seals and amulets.
Field identification & locations
Identify by its hardness (will scratch glass) and smooth, water-worn exterior. Commonly found in riverbeds, gravel pits, and coastal areas. High silica content makes it resistant to weathering.
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