larvikite

Larvikite is a coarse-grained igneous rock belonging to the feldspathoid group. It is primarily found in Larvik, Norway, and is known for its distinctive iridescent blue or gray flashes, a phenomenon called schiller or labradorescence. This optical effect is caused by the light reflecting off lamellar inclusions within the feldspar crystals. The main minerals in larvikite are alkali feldspar, particularly albite and orthoclase, along with smaller amounts of nepheline, augite, and biotite. The characteristic blue shimmer is due to the diffraction of light by these microscopic inclusions.

The rock's unique appearance has made it a popular material for decorative purposes, particularly in interior design and monumental stonework. It is often used for countertops, wall cladding, and ornamental features. Its durability and resistance to weathering also contribute to its suitability for outdoor applications. Larvikite is sometimes mistakenly referred to as labradorite, although labradorite is a different mineral within the plagioclase feldspar series that exhibits a similar optical effect. The geological formation of larvikite is associated with alkaline intrusive igneous activity. Its discovery and commercial exploitation began in the early 20th century, leading to its widespread use in architecture and design worldwide.