igneous
Dalmatian jasper
Quartz-bearing, orbicular microcrystalline silica (commonly sold as “Dalmatian jasper”; often an altered porphyritic igneous rock)
AI-generated identification · may be incorrectCream to pale gray matrix with black, rounded spots; opaque, fine-grained, waxy to dull luster, no visible cleavage, and typical hardness about 6.5–7 Mohs. The dark spots are usually amphibole or tourmaline-group minerals, though commercial material is variably identified.
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Physical properties
Cream to pale gray matrix with black, rounded spots; opaque, fine-grained, waxy to dull luster, no visible cleavage, and typical hardness about 6.5–7 Mohs. The dark spots are usually amphibole or tourmaline-group minerals, though commercial material is variably identified.
Formation & geological history
Most specimens are quarried in Mexico and formed through volcanic or subvolcanic processes followed by alteration and silicification; it is not a true jasper in the strict mineralogical sense. Exact geological age varies by deposit.
Uses & applications
Cut and polished for beads, cabochons, carvings, worry stones, and decorative objects; rarely used for construction because it is sold mainly as lapidary material.
Geological facts
Its distinctive black-on-cream pattern resembles a Dalmatian dog, giving the trade name. The pictured pieces appear broken or roughly cut rather than naturally weathered.
Field identification & locations
Identify by the opaque cream base, sharply contrasting black spots, fine texture, and lack of glassy crystals; confirm with a scratch test only on an inconspicuous area. Commonly found in lapidary shops and Mexican mineral markets.
