igneous
Dalmatian jasper
Orbicular rhyolite, commonly sold as Dalmatian jasper; quartz- and feldspar-rich volcanic rock with dark amphibole/biotite inclusions
AI-generated identification · may be incorrectCream to tan fine-grained groundmass with distinctive rounded black spots; opaque, matte to waxy luster, no visible cleavage, hardness about 6–7 Mohs, and specific gravity roughly 2.5–2.7.
Identified More igneous →
Explore Dalmatian jasper in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Cream to tan fine-grained groundmass with distinctive rounded black spots; opaque, matte to waxy luster, no visible cleavage, hardness about 6–7 Mohs, and specific gravity roughly 2.5–2.7.
Formation & geological history
A trade name for a spotted rhyolite, likely formed from silica-rich volcanic lava containing mafic mineral inclusions; generally Cenozoic volcanic material, especially associated with deposits in Mexico.
Uses & applications
Commonly cut and polished for cabochons, beads, carvings, tumbled stones, and decorative objects; not usually used as a major construction stone.
Geological facts
Despite its name, it is not true jasper in the strict mineralogical sense and is unrelated to Dalmatian dogs; the black markings are mineral inclusions rather than painted spots.
Field identification & locations
Identify it by its cream base, naturally irregular black inclusions, fine texture, and ability to take a good polish; distinguish it from dyed or synthetic spotted materials by inspecting scratches and broken surfaces.
