metamorphic
Red jasper
Jasper, microcrystalline quartz (SiO₂) colored mainly by iron oxides
AI-generated identification · may be incorrectOpaque brick-red to reddish-brown, fine-grained, typically dull to waxy or vitreous when polished; hardness about 6.5–7 Mohs, no cleavage, conchoidal fracture, and specific gravity around 2.5–2.7. The specimen appears polished or naturally smoothed, with possible darker iron-rich banding.
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Physical properties
Opaque brick-red to reddish-brown, fine-grained, typically dull to waxy or vitreous when polished; hardness about 6.5–7 Mohs, no cleavage, conchoidal fracture, and specific gravity around 2.5–2.7. The specimen appears polished or naturally smoothed, with possible darker iron-rich banding.
Formation & geological history
Forms when silica-rich fluids cement or replace sediments and volcanic rocks, incorporating hematite or goethite that produces the red color; commonly Precambrian to younger. It is found in hydrothermal veins, volcanic terrains, and iron-rich sedimentary deposits.
Uses & applications
Used for beads, cabochons, carvings, ornaments, and inexpensive lapidary items; crushed jasper may be used as decorative aggregate. Its value is primarily aesthetic and collectible rather than industrial.
Geological facts
Jasper is a variety of chalcedony or microcrystalline quartz, though the term is also used broadly for opaque silica-rich rocks. Red coloration generally indicates finely dispersed hematite.
Field identification & locations
Identify it by its opaque red color, very fine texture, lack of visible crystals, and ability to scratch glass; a streak test is usually pale red to brown. Common sources include India, Madagascar, Brazil, Australia, and the western United States.
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