sedimentary (secondary classification: cryptocrystalline quartz)
Jasper pebble
Silicon dioxide (SiO2) with iron oxide inclusions
Hardness: 6.5–7 on Mohs scale. Color: Reddish-brown to maroon due to hematite/iron content. Luster: Dull to waxy when unpolished. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.58–2.91.
- Hardness
- 6
- Color
- Reddish-brown to maroon due to hematite/iron content
- Luster
- Dull to waxy when unpolished
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: Reddish-brown to maroon due to hematite/iron content. Luster: Dull to waxy when unpolished. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.58–2.91.
Formation & geological history
Formed from the deposition of silica in fluid-rich environments, often near volcanic ash or in sedimentary beds where silica-rich fluids permeate porous ground. The color comes from iron impurities during its millions of years of formation.
Uses & applications
Commonly used in lapidary work, jewelry (cabochons), river rock landscaping, and as a 'pocket stone' for collectors.
Geological facts
Jasper has been used since antiquity as a gemstone. The word is derived from the Greek 'iaspis', meaning 'spotted stone.' Many cultures believed it had protective properties and helped ground the wearer.
Field identification & locations
Identify in the field by its opacity (it will not let light through even when thin) and its smooth, rounded texture in riverbeds. Found globally in river wash and gravel deposits. Collectors look for unique patterns or deep, consistent colors.
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