sedimentary or metamorphic
Jasper
Chalcedony (Microcrystalline Quartz) - SiO2
Hardness: 6.5-7. Color: multicolored, often red, green, yellow, brown. Luster: Vitreous to dull. Crystal structure: Trigonal (microcrystalline). Smooth, rounded surface due to water tumbling.
- Hardness
- 6
- Color
- multicolored, often red, green, yellow, brown
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7. Color: multicolored, often red, green, yellow, brown. Luster: Vitreous to dull. Crystal structure: Trigonal (microcrystalline). Smooth, rounded surface due to water tumbling.
Formation & geological history
Forms in sedimentary environments or as a secondary mineral in volcanic rock cavities. Silica-rich fluids percolate through rock, precipitating microcrystalline quartz and incorporating impurities (like iron oxides) that give it color. The rounded shape indicates transport and weathering by water, likely found in a riverbed or on a beach.
Uses & applications
Commonly used for lapidary arts, tumbling, cabochons, and ornamental carving. historically used for tools and weapons due to its hardness and conchoidal fracture.
Geological facts
Jasper is an opaque, impure variety of silica. The name means 'spotted or speckled stone'.
Field identification & locations
Identify by its hardness (scratches glass), opacity, and conchoidal fracture. Often found as rounded river rocks or beach cobbles. Commonly found worldwide in areas with volcanic or sedimentary history.
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