igneous
Dalmatian jasper (likely orbicular microgranite)
Quartz–feldspar–biotite/pyroxene microgranite; commonly marketed as Dalmatian jasper
AI-generated identification · may be incorrectFine-grained pale gray matrix with rounded black spots, glassy to dull luster, and no obvious cleavage; hardness about 6–7 Mohs, specific gravity roughly 2.6–2.8. The spots are typically dark amphibole, biotite, or arfvedsonite minerals rather than true jasper inclusions.
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Physical properties
Fine-grained pale gray matrix with rounded black spots, glassy to dull luster, and no obvious cleavage; hardness about 6–7 Mohs, specific gravity roughly 2.6–2.8. The spots are typically dark amphibole, biotite, or arfvedsonite minerals rather than true jasper inclusions.
Formation & geological history
Forms from silica-rich magma that cooled slowly beneath Earth’s surface, producing a fine-grained granitic rock; the commercial material is especially associated with Chihuahua, Mexico, and is generally Mesozoic to Cenozoic in age.
Uses & applications
Used for cabochons, beads, carvings, tumbled stones, and ornamental objects; less commonly used as dimension stone because it is usually sold in small pieces.
Geological facts
“Dalmatian jasper” is a lapidary trade name, not a strict mineralogical classification. Its distinctive black-on-cream pattern resembles a Dalmatian dog coat.
Field identification & locations
Identify it by the cream feldspathic groundmass and irregular black mineral spots; test hardness on an inconspicuous edge and inspect with a loupe for interlocking grains. Common sources include Chihuahua, Mexico, and similar granitic terrains.
