sedimentary
Jasper
Jasper (Silica/Silicon Dioxide, SiO2)
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, dull green, earthy; Luster: Dull to greasy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.5-2.9.
- Hardness
- 6
- Color
- Reddish-brown, dull green, earthy
- Luster
- Dull to greasy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, dull green, earthy; Luster: Dull to greasy; Crystal Structure: Microcrystalline/Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.5-2.9.
Formation & geological history
Formed through the accumulation of fine-grained silica in hydrothermal veins or sedimentary environments. Iron oxides often provide the reddish hues. This specimen appears to have a weathered outer surface with green and red mineral zones.
Uses & applications
Used primarily as decorative gemstones, in jewelry (cabochons), as an industrial abrasive, and for ornamental stone carvings.
Geological facts
Jasper is an opaque variety of chalcedony. It has been used by humans for thousands of years, including for making early stone tools due to its hardness and sharp edges when fractured.
Field identification & locations
Identify by its hardness (it will scratch glass), opaque nature, and smooth, curved (conchoidal) fracture lines on fresh surfaces. Often found in riverbeds or areas with volcanic activity.
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