Spectrolite

Spectrolite exhibits a richer range of colors than other labradorites as for instance in Canada or Madagascar (which show mostly tones of blue-grey-green) and high labradorescence.[1][2] The term is sometimes incorrectly used to describe labradorite whenever a richer display of colors is present, regardless of locality. Due to the unique colors mined in Finland, spectrolite has become a brand name for material mined only there. Sometimes spectrolite is incorrectly used to describe labradorite whenever a richer display of colors is present, regardless of locality: for example, labradorite with the spectrolite play of colors has sometimes described material from Madagascar.[1]

The difference between Finnish spectrolite and other labradorites is that crystals of the former have considerably stronger and larger colourfulness, caused by its opaque base color; other labradorites have a transparent base color. The anorthosite-dominant plagioclase from Ylämaa, Finland was named by Walter Mikkola and then accepted as a commercial name by geology professor Aarne Laitakari, then director of Geological Survey of Finland. Spectrolite is often cut as a lapidary cabochon, similar to plain labradorite, to enhance the effect and is used as a gemstone.

Finnish geologist Aarne Laitakari (1890–1975) described the peculiar stone and sought its origin for years when his son Pekka discovered a deposit at Ylämaa in south-eastern Finland, while building the Salpa Line fortifications there in 1940.

The quarrying of spectrolite began after the Second World War and became a significant local industry. In 1973, the first workshop in Ylämaa began cutting and polishing spectrolite for jewels. After that, a gem center was established in Ylämaa with training for gem-cutting accompanied by an annual Gem and Mineral Show initiated by Esko Hämäläinen, mayor of Ylämaa municipality.

Seppo Lahti I.1989 The origin of interference colours in spectrolite (iridescent labradorite).Geologi 41.