sedimentary
Jasper (Sedimentary variety)
Silicon Dioxide (SiO2) with impurities
Hardness: 6.5–7 on Mohs scale. Color: Reddish-brown with swirled, earthy patterns. Luster: Dull to waxy when unpolished. Crystal Structure: Microcrystalline/cryptocrystalline (trigonal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58–2.91.
- Hardness
- 6
- Color
- Reddish-brown with swirled, earthy patterns
- Luster
- Dull to waxy when unpolished
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: Reddish-brown with swirled, earthy patterns. Luster: Dull to waxy when unpolished. Crystal Structure: Microcrystalline/cryptocrystalline (trigonal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58–2.91.
Formation & geological history
Formed through the deposition of silica from water-rich environments, often as a result of volcanic ash or radiolarian ooze undergoing lithification. The red color suggests significant iron oxide (hematite) content during formation. Age varies by locale but can range back to the Proterozoic Era.
Uses & applications
Primarily used for lapidary work, jewelry (cabochons), and as an ornamental stone. Significant historical use for making tools/arrowheads due to its conchoidal fracturing.
Geological facts
Jasper is an opaque variety of chalcedony. The swirled patterns in this specimen often occur from fluid movement or pressure during the dehydration process of the silica gel precursor. It has been used since antiquity for seals and amulets in Mesopotamia and Egypt.
Field identification & locations
Identify in the field by its hardness (it will scratch glass) and its opaque quality when held to light. Common in iron-rich sedimentary deposits. For collectors, look for high-contrast banding or unique scenic patterns.
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