igneous
Jasper in Rhyolite matrix
Silicon Dioxide (SiO2) with various inclusions in Felsic Igneous matrix
Hardness: 6.5-7 (Mohs scale); Color: Red/brown (Jasper) and grey/green (Rhyolite); Luster: Subvitreous to dull; Crystal structure: Cryptocrystalline; Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Red/brown (Jasper) and grey/green (Rhyolite)
- Luster
- Subvitreous to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Red/brown (Jasper) and grey/green (Rhyolite); Luster: Subvitreous to dull; Crystal structure: Cryptocrystalline; Specific Gravity: 2.58-2.91
Formation & geological history
Formed from silica-rich volcanic eruptions where high-silica lava cools quickly (Rhyolite phase) while silica-rich fluids permeate cracks and cavities to form Jasper deposits, common in Cenozoic volcanic fields.
Uses & applications
Used primarily for lapidary work, cabochons for jewelry, decorative garden stones, and as a specimen for geological education and collecting.
Geological facts
Jasper is often referred to as 'the supreme nurturer' in metamorphic folklore; the red coloration in this specimen is caused by iron inclusions within the microcrystalline quartz.
Field identification & locations
Identify in the field by its fine-grained, 'sugary' or matte texture and high hardness (it will scratch glass). Commonly found in the Western United States, particularly Oregon and Idaho, and parts of Australia.
