igneous
Tumbled Dalmatian jasper
Quartz-rich alkali rhyolite, commonly marketed as Dalmatian jasper; chiefly quartz, feldspar, and dark amphibole/biotite inclusions
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; cream to pinkish-white with black spots, opaque, and generally dull to waxy after tumbling. Fine-grained, massive texture with no obvious cleavage; specific gravity roughly 2.6–2.7.
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Physical properties
Hardness about 6.5–7 Mohs; cream to pinkish-white with black spots, opaque, and generally dull to waxy after tumbling. Fine-grained, massive texture with no obvious cleavage; specific gravity roughly 2.6–2.7.
Formation & geological history
A silica-rich volcanic rock formed when rhyolitic magma cooled rapidly, with dark mineral inclusions producing the spotted pattern; generally Cenozoic in age. Commercial material is especially associated with Chihuahua, Mexico.
Uses & applications
Used for polished stones, cabochons, beads, carvings, and decorative objects; it has modest gemstone and collecting value rather than major industrial significance.
Geological facts
“Dalmatian jasper” is a trade name, not necessarily true jasper—a form of spotted rhyolite is the usual material. The black markings are commonly interpreted as amphibole-group minerals, aegirine, or other mafic inclusions.
Field identification & locations
Identify it by its opaque ivory-to-pink body, irregular black spots, fine volcanic texture, and glass-scratching hardness; distinguish it from spotted granite by its smoother, more uniform fine grain. Commonly found as tumbled material from Mexico.
