igneous
Tumbled black-and-white stone, likely dalmatian jasper
Quartz-rich porphyritic rhyolite (commercially called dalmatian jasper), with black aegirine/arfvedsonite-like inclusions
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; cream-white fine-grained matrix with rounded black inclusions, opaque, and dull to slightly vitreous luster. The rounded shape indicates tumbling and polishing; exact mineral identification requires testing or microscopy.
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Physical properties
Hardness about 6.5–7 Mohs; cream-white fine-grained matrix with rounded black inclusions, opaque, and dull to slightly vitreous luster. The rounded shape indicates tumbling and polishing; exact mineral identification requires testing or microscopy.
Formation & geological history
Usually formed from silica-rich volcanic lava that cooled rapidly, trapping dark mineral inclusions; likely Cenozoic volcanic material from Mexico, though locality varies by seller. It is not true jasper in the strict geological sense.
Uses & applications
Used for inexpensive cabochons, beads, carvings, decorative stones, and mineral collections; unsuitable for major construction because specimens are small and decorative.
Geological facts
The trade name “dalmatian jasper” refers to its spotted appearance resembling a Dalmatian dog, not to an animal or fossil. Some commercially similar stones are altered rhyolite or other volcanic rocks.
Field identification & locations
Identify by the cream rhyolitic groundmass, irregular black spots, lack of banding, and glass-scratching hardness; a streak test and magnification help distinguish it from dyed stones. Commonly sold from Mexico and worldwide lapidary markets.
