sedimentary
Jasper
Jasper (Silicon Dioxide, SiO2)
Hardness: 6.5-7 (Mohs scale), Color: Red to brownish-orange (due to iron inclusions), Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline/cryptocrystalline), 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: Red to brownish-orange (due to iron inclusions), Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline/cryptocrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.58-2.91
Formation & geological history
Formed through the deposition of silica from mineral-rich waters or volcanic ash, which then undergoes metamorphism or replaces organic matter and other minerals. Often associated with Banded Iron Formations.
Uses & applications
Used primarily for semi-precious jewelry (cabochons, beads), decorative lapidary work, ornaments, and historically for seal-making and tools.
Geological facts
Jasper is an opaque variety of chalcedony. The name stems from the Greek 'iaspis', meaning spotted stone. It has been used by humans for thousands of years, notably by the Hittites and ancient Egyptians.
Field identification & locations
Identify in the field by its opacity (it will not let light through even at thin edges, unlike agate), its hardness (will scratch glass), and its distinctive conchoidal fracture. Common in gravel beds and desert regions.
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