sedimentary
Jasper with Quartz inclusion
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness: 6.5 - 7 on the Mohs scale. Color: Opaque tan/white with dark matrix. Luster: Waxy to vitreous. Crystal structure: Trigonal/Microcrystalline. Specific gravity: 2.6 - 2.9.
- Hardness
- 6
- Color
- Opaque tan/white with dark matrix
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5 - 7 on the Mohs scale. Color: Opaque tan/white with dark matrix. Luster: Waxy to vitreous. Crystal structure: Trigonal/Microcrystalline. Specific gravity: 2.6 - 2.9.
Formation & geological history
Formed from silica-rich fluids percolating through sedimentary rocks or volcanic ash, often during the Proterozoic to Cenozoic eras. The central feature suggests a geode-like cavity filling where quartz crystals precipitated late in the stone's formation.
Uses & applications
Commonly used for lapidary work (cabochons), river rock landscaping, aquarium decor, and as 'pocket stones' for collectors. Hard enough for tumbling and polishing to a high gloss.
Geological facts
Jasper is an impure variety of silica; the different colors are caused by mineral inclusions like iron oxide. The term comes from the Greek 'iaspis', meaning 'spotted stone.' Many tumbled river jaspers show unique 'bullseye' or 'eye' patterns like the specimen pictured.
Field identification & locations
Identify in the field by its smoothness (water-worn), hardness (it will scratch glass), and opacity. Common in riverbeds and coastal regions worldwide, especially in the Western United States and India.
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