igneous
Dalmatian Jasper
Peralkaline Quartz-Feldspar Igneous Rock with Arfvedsonite
AI-generated identification · may be incorrectHardness: 5.5-7 (Mohs); Color: Pale grey or cream base with distinct black or dark green circular spots; Luster: Vitreous to dull; Crystal structure: Microcrystalline; Specific gravity: 2.58-2.91.
- Hardness
- 5
- Luster
- Vitreous to dull
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Physical properties
Hardness: 5.5-7 (Mohs); Color: Pale grey or cream base with distinct black or dark green circular spots; Luster: Vitreous to dull; Crystal structure: Microcrystalline; Specific gravity: 2.58-2.91.
Formation & geological history
Formed during volcanic activity where magma cools quickly, containing quartz, feldspar, and minerals like arfvedsonite that crystallize into spots. Despite its name, it is a rock (peralkaline rhyolite) rather than a true chalcedony-based jasper.
Uses & applications
Used extensively in jewelry for beads, cabochons, and tumbled stones. Also popular in lapidary carving and metaphysical collecting.
Geological facts
The 'spots' in Dalmatian Jasper were long thought to be tourmaline, but recent studies have confirmed they are actually the amphibole mineral arfvedsonite. It is named after the Dalmatian dog breed because of its similar spotted appearance.
Field identification & locations
Identified by its cream-colored groundmass and uniform black spot distribution. Primarily mined in Chihuahua, Mexico. Collectors should look for even spotting and a high-quality polish which reveals the unique texture.
