sedimentary
Brown Jasper / Chert Pebbles
Microcrystalline Quartz (SiO2) with iron oxide impurities
Hardness: 6.5-7 Mohs; Color: Chocolate brown to dark tan with mottled patterns; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Chocolate brown to dark tan with mottled patterns
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 Mohs; Color: Chocolate brown to dark tan with mottled patterns; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9
Formation & geological history
Formed from the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments. Its brown color is typically due to the presence of goethite or limonite (iron oxides). This specimen is a rounded river pebble, shaped by water erosion.
Uses & applications
Commonly used as decorative landscaping stones, aquarium gravel, or tumbled for use in low-cost folk jewelry and pocket stones.
Geological facts
Jasper is an opaque variety of chalcedony. Brown jasper is often referred to as Egyptian Marble in older archaeological texts. It has been used for making seal stones and amulets since antiquity.
Field identification & locations
Identify in the field by its high hardness (it will scratch glass), smooth waxy feel when wet, and lack of visible grains. Found globally in river beds and beaches, particularly in silica-rich sedimentary basins.
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