sedimentary
Jasper
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5-7 (Mohs scale); Color: Red, brown, or variegated; Luster: Dull to greasy; Crystal Structure: Microcrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91
- Hardness
- 6
- Color
- Red, brown, or variegated
- Luster
- Dull to greasy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Red, brown, or variegated; Luster: Dull to greasy; Crystal Structure: Microcrystalline (Trigonal); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.58-2.91
Formation & geological history
Formed from silica-rich fluids and sedimentary processes, or in volcanic ash, often associated with hydrothermal circulation or diagenesis of silica-rich marine sediments.
Uses & applications
Used primarily in lapidary work, jewelry (cabochons), interior decoration, and as a historic source for stone tools due to its durability and sharp edges when broken.
Geological facts
Jasper has been a favorite gemstone since antiquity; it was used to create cylinder seals in Mesopotamia and is mentioned in various historical texts as a protective stone.
Field identification & locations
Identified by its waxy-to-dull luster, extreme hardness (it will scratch glass), and characteristic conchoidal fracture (smooth, curved breaks). Common in river beds and desert environments.
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