sedimentary
Jasper
Jasper (Silicon Dioxide, SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Variegated reds/browns/creams, Luster: Vitreous to waxy, Structure: Cryptocrystalline/Microcrystalline, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.58-2.91
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: Variegated reds/browns/creams, Luster: Vitreous to waxy, Structure: Cryptocrystalline/Microcrystalline, Cleavage: None (Conchoidal fracture), Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the deposition of silica-rich fluids in volcanic ash or sedimentary environments, often involving secondary mineralization and hydrothermal processes. Ages vary globally from Precambrian to more recent eras.
Uses & applications
Used primarily in lapidary arts for jewelry, decorative objects, tumbled stones, and as an ornamental gemstone. Historically used for seal stones and tools.
Geological facts
The name comes from the Old French word 'jaspre', meaning 'spotted stone'. It is an opaque variety of chalcedony that contains up to 20% impurities, which create its unique color patterns.
Field identification & locations
Identify in the field by its hardness (scratches glass), opaque nature, and smooth, waxy feel when polished or tumbled. Often found in riverbeds or coastal deposits as rounded pebbles.
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