sedimentary
Jasper
Jasper (Cryptocrystalline variety of Quartz, SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Red, orangish-brown, or multicolored due to iron inclusions; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture
- Hardness
- 6
- Color
- Red, orangish-brown, or multicolored due to iron inclusions
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Red, orangish-brown, or multicolored due to iron inclusions; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None, exhibits conchoidal fracture
Formation & geological history
Formed through the deposition of silica from water or hydrothermal fluids, often in environments where volcanic ash or sedimentary layers are present. The red color is typically due to iron oxidation.
Uses & applications
Used primarily for jewelry (cabochons, beads), decorative lapidary arts, and ornamental stone carvings. Historically used for making tools and seals.
Geological facts
Jasper has been used as a gemstone since antiquity and is mentioned in various historical texts including the Bible. It is a dense, opaque variety of chalcedony.
Field identification & locations
Identify by its opacity (unlike translucent agate) and its hardness—it cannot be scratched by a steel knife. Frequently found as river-worn pebbles like the specimen in the image.
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