igneous
Dalmatian Jasper
Peralkaline rhyolite
Hardness: 6.5-7 (Mohs); Color: Creamy tan or yellowish-brown groundmass with black/dark green spots; Luster: Vitreous to waxy; Crystal structure: Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Luster
- Vitreous to waxy
Identified More igneous →
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Creamy tan or yellowish-brown groundmass with black/dark green spots; Luster: Vitreous to waxy; Crystal structure: Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through volcanic processes where silica-rich lava cools quickly. The black spots were originally thought to be tourmaline but are increasingly identified as the amphibole mineral arfvedsonite. Most specimens originate from Mexico.
Uses & applications
Primarily used in the jewelry industry for beads, cabochons, and carvings. It is also a popular stone for tumbling and metaphysical collections.
Geological facts
Despite its common trade name 'Dalmatian Jasper,' it is technically an igneous rock (rhyolite) rather than a true sedimentary jasper. The black spots are minerals that crystallized within the cooling magma.
Field identification & locations
Identify by its distinctive black-on-tan spotted appearance resembling a Dalmatian dog. Look for a smooth, hard surface that cannot be scratched by a steel knife. Commonly found in Chihuahua, Mexico.
