igneous
Larvikite
Larvikite (anorthosite–monzonitic feldspathic rock; commonly rich in labradorite)
AI-generated identification · may be incorrectMedium- to coarse-grained, dark gray stone with blue-silver iridescent feldspar flashes, black amphibole/pyroxene, and minor biotite; hardness about 6–6.5, glassy to pearly luster, massive texture, and feldspar cleavage. The blue sheen is labradorescence, not surface paint.
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Physical properties
Medium- to coarse-grained, dark gray stone with blue-silver iridescent feldspar flashes, black amphibole/pyroxene, and minor biotite; hardness about 6–6.5, glassy to pearly luster, massive texture, and feldspar cleavage. The blue sheen is labradorescence, not surface paint.
Formation & geological history
A slowly cooled intrusive igneous rock formed from feldspar-rich magma, chiefly in the Permian Oslo Rift of southeastern Norway, roughly 300 million years ago. Similar labradorescent rocks occur elsewhere, but Norwegian larvikite is the classic source.
Uses & applications
Used as polished architectural stone, countertops, monuments, tiles, and decorative objects; attractive hand specimens are popular with collectors.
Geological facts
Its signature blue flash results from light interference within intergrown feldspar crystals. Commercial larvikite is often marketed as “Blue Pearl” or “Emerald Pearl” granite, although it is not true granite.
Field identification & locations
Identify it by coarse interlocking crystals, dark gray body, and blue feldspar flashes that change with viewing angle; a polished surface enhances the effect. Commonly found around Larvik, Norway.
