sedimentary
Jasper
Silicon Dioxide (SiO2) with iron oxide impurities
Hardness: 6.5–7 on the Mohs scale. Color: Highly variable, featuring deep red and mustard yellow tones. Luster: Dull to waxy when raw, vitreous when polished. Crystal structure: Microcrystalline/cryptocrystalline (Trigonal). Cleavage: None; exhibits conchoidal fracture. Specific gravity: 2.58–2.91.
- Hardness
- 6
- Color
- Highly variable, featuring deep red and mustard yellow tones
- Luster
- Dull to waxy when raw, vitreous when polished
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Physical properties
Hardness: 6.5–7 on the Mohs scale. Color: Highly variable, featuring deep red and mustard yellow tones. Luster: Dull to waxy when raw, vitreous when polished. Crystal structure: Microcrystalline/cryptocrystalline (Trigonal). Cleavage: None; exhibits conchoidal fracture. Specific gravity: 2.58–2.91.
Formation & geological history
Jasper is an opaque variety of chalcedony. It forms when silica-rich fluids permeate through volcanic ash or sedimentary rocks, precipitating out over long geological periods. The vibrant red and yellow colors in this specimen are caused by the presence of hematite (red) and goethite or limonite (yellow).
Uses & applications
Used primarily as a gemstone for jewelry (cabochons, beads), decorative ornaments, and lapidary art. Historically used for making tools and seals due to its hardness and lack of cleavage.
Geological facts
Jasper has been used throughout human history; it was a favorite gem in the ancient world, mentioned in the Bible and used by Babylonian and Minoan cultures. The term comes from the Greek 'iaspis', meaning 'spotted stone'.
Field identification & locations
Identify in the field by its hardness (it will scratch glass), opaque nature (it does not let light through even at thin edges), and conchoidal fracture patterns. Commonly found in riverbeds or coastal areas in the Western United States, India, and Brazil.
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