igneous
Polished black-and-white feldspathic stone, likely larvikite or gabbro
Larvikite (plagioclase feldspar–augite–nepheline assemblage), possibly coarse gabbro
AI-generated identification · may be incorrectHardness about 6–7 Mohs; gray-black with creamy white feldspar, polished vitreous to pearly luster, coarse interlocking crystals, and no obvious cleavage on the surface. Dense, typically about 2.7–3.0 specific gravity.
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Physical properties
Hardness about 6–7 Mohs; gray-black with creamy white feldspar, polished vitreous to pearly luster, coarse interlocking crystals, and no obvious cleavage on the surface. Dense, typically about 2.7–3.0 specific gravity.
Formation & geological history
A slowly cooled intrusive igneous rock formed from magma deep in the crust, generally Paleozoic to Mesozoic depending on locality; larvikite is especially associated with Permian intrusions in Norway.
Uses & applications
Used as a decorative dimension stone, countertops, paving, and polished lapidary material; attractive pieces are sold as cabochons or worry stones.
Geological facts
The pale areas are likely feldspar, while dark grains are pyroxene or amphibole; the bright mottled effect is characteristic of polished coarse-grained intrusive rocks.
Field identification & locations
Identify it by its high density, interlocking coarse texture, and feldspar-rich black-gray pattern; larvikite commonly comes from the Larvik region of Norway, whereas similar gabbro occurs worldwide. A small polished specimen is typically worth $5–$25, with exceptional jewelry-grade pieces reaching $30–$75.
