Spectrolite

Spectrolite is an uncommon variety of labradorite feldspar.

Spectrolite from Ylämaa, Finland
Polished spectrolite showing the color play

Colors

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]

Finland deposit

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.

History

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.

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gollark: Am I better at resisting peer pressure than other people: well, I'd *like* to think so, but so would probably everyone else ever.
gollark: Anyway, I have, I think, reasonably strong "no genocide" ethics. But I don't know if, in a situation where everyone seemed implicitly/explicitly okay with helping with genocides, and where I feared that I would be punished if I either didn't help in some way or didn't appear supportive of helping, I would actually stick to this, since I don't think I've ever been in an environment with those sorts of pressures.
gollark: Maybe I should try arbitrarily increasing the confusion via recursion.
gollark: If people are randomly assigned (after initial mental development and such) to an environment where they're much more likely to do bad things, and one where they aren't, then it seems unreasonable to call people who are otherwise the same worse from being in the likely-to-do-bad-things environment.I suppose you could argue that how "good" you are is more about the change in probability between environments/the probability of a given real world environment being one which causes you to do bad things. But we can't check those with current technology.

References

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

  1. Michael O'Donoghue, Gems, Butterworth-Heinemann, 6th ed., 2006, pp. 238-267, ISBN 0-7506-5856-8
  2. Walter Schumann, Gemstones of the World, Sterling, 3rd ed., 2007, pp. 52 - 53, 182 ISBN 1-4027-4016-6


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