igneous
Dalmatian Jasper
Peralkaline Quartz Feldspar Porphyry
Hardness: 5.5-7 (Mohs scale), Color: Creamy white to pale gray background with black or dark brown spots, Luster: Vitreous to dull, Crystal structure: Microcrystalline quartz with amphibole inclusions, Cleavage: None
- Hardness
- 5
Identified More igneous →
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Physical properties
Hardness: 5.5-7 (Mohs scale), Color: Creamy white to pale gray background with black or dark brown spots, Luster: Vitreous to dull, Crystal structure: Microcrystalline quartz with amphibole inclusions, Cleavage: None
Formation & geological history
Formed from volcanic activity where igneous rock (like aplite or rhyolite) solidified. The black spots are inclusions of arfvedsonite or other amphibole minerals that cooled within the matrix. Most commercial specimens originate from Chihuahua, Mexico.
Uses & applications
Primarily used for lapidary work, including cabochons, beads, decorative carvings, and tumbled stones for aquarium decor or metaphysical collections.
Geological facts
Despite being named 'Jasper,' it is actually an igneous rock (porphyry) rather than a true sedimentary jasper. The black spots were long thought to be tourmaline, but are now confirmed to be the mineral arfvedsonite.
Field identification & locations
Identify by the distinct 'Dalmatian dog' spotted pattern. It is rarely found in the wild outside of specific mining locations in Mexico. Collectors should look for a uniform cream base and sharp contrast with the black spots.
