igneous
Dalmatian jasper
Porphyritic microcrystalline quartz-rich rock, commonly sold as Dalmatian jasper; spots are chiefly arfvedsonite/amphibole minerals, sometimes altered feldspar
AI-generated identification · may be incorrectBlack-and-cream, opaque, smoothly polished, with a dull to vitreous luster; quartz-rich matrix has Mohs hardness about 6.5–7, no obvious cleavage, and fine-grained microcrystalline structure. The rounded form indicates tumbling or polishing.
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Physical properties
Black-and-cream, opaque, smoothly polished, with a dull to vitreous luster; quartz-rich matrix has Mohs hardness about 6.5–7, no obvious cleavage, and fine-grained microcrystalline structure. The rounded form indicates tumbling or polishing.
Formation & geological history
Typically sourced from alkaline igneous rocks near Chihuahua, Mexico, where dark amphibole-rich inclusions occur in a pale feldspathic or quartz-bearing matrix. It formed from cooling volcanic to shallow intrusive magma, likely in the Cenozoic, though exact locality and age vary.
Uses & applications
Used for cabochons, beads, carvings, palm stones, and decorative objects; it has little industrial importance beyond ornamental stone.
Geological facts
Despite its trade name, Dalmatian jasper is generally not true jasper because its matrix is not dominantly chalcedony. The leopard-like pattern is its principal identifying feature.
Field identification & locations
Identify it by the distinctive mustard-colored rounded spots on a black, fine-grained background and its opaque, hard, polished surface; avoid confusing it with spotted basalt or man-made composite. Commonly found in lapidary markets from Mexico.
