sedimentary
Jasper
Silicon dioxide (SiO2)
Hardness of 6.5–7 on the Mohs scale. Opaque appearance with a subvitreous to waxy luster. Microcrystalline structure. Colors range from tan, brown, and yellow to reddish-orange due to iron inclusions. Conchoidal fracture.
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Physical properties
Hardness of 6.5–7 on the Mohs scale. Opaque appearance with a subvitreous to waxy luster. Microcrystalline structure. Colors range from tan, brown, and yellow to reddish-orange due to iron inclusions. Conchoidal fracture.
Formation & geological history
Formed through the accumulation of fine-grained silicate minerals and volcanic ash, or by the replacement of organic materials with silica. Found in various geological ages often in sedimentary or metamorphic layers.
Uses & applications
Used primarily in lapidary work for jewelry, cabochons, and beads. Also collected as decorative stream-tumbled stones or used in home decor.
Geological facts
Jasper is an impure variety of silica. The name 'Jasper' is derived from the Greek word 'iaspis', meaning spotted stone. It is a major component in Banded Iron Formations.
Field identification & locations
Identify by its opacity (unlike translucent agate) and its hardness—it cannot be scratched by a steel knife. Commonly found in riverbeds, gravel bars, and desert washes. Smooth, water-worn surfaces are typical for river-recovered specimens.
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