igneous
Larvikite cabochon
Larvikite, a feldspar-rich monzonitic intrusive rock; commonly containing blue labradorescent alkali feldspar, nepheline, and dark pyroxene/biotite
AI-generated identification · may be incorrectHardness about 6–6.5 Mohs; gray to blue-gray with black mineral patches and blue flash, vitreous to pearly luster, granular interlocking crystals, and no prominent cleavage as a rock. The pictured specimen is polished and teardrop-shaped.
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Physical properties
Hardness about 6–6.5 Mohs; gray to blue-gray with black mineral patches and blue flash, vitreous to pearly luster, granular interlocking crystals, and no prominent cleavage as a rock. The pictured specimen is polished and teardrop-shaped.
Formation & geological history
Formed by slow cooling of alkaline magma roughly 290–300 million years ago, especially in the Permian Oslo Rift of southeastern Norway. Its blue sheen results from light interference in feldspar crystals.
Uses & applications
Used as decorative and architectural stone, countertops, monuments, and polished cabochons. Attractive blue flash gives quality pieces modest jewelry and collector appeal.
Geological facts
Larvikite is Norway’s national rock and is often marketed as “blue pearl granite,” although it is not true granite. Similar-looking specimens may be labradorite-rich rocks or indigo gabbro.
Field identification & locations
Identify by the coarse gray-black body, abundant blue iridescent feldspar flashes, and black pyroxene-rich patches; fresh surfaces reveal interlocking grains. Major sources include Larvik, Norway, with related rocks in alkaline intrusive complexes worldwide.
