LARVIKITE

( Fr- larvikite; Ger- Larvikit; Nor- larvikitt; Rus- )

LARVIKITE (also spelled laurvikite)

A. Larvikite, two larger blocks, usually marketed as "Norwegian Pearl granite." In some marketplaces, the lighter variety (left) is called "Blue Norwegian moonstone" and the darker variety (right) as "Royal blue pearl granite" or "Emerald pearl ..." The small piece (height - 3.5 cm) on top of the left block is anorthosite (see ANORTHOSITE entry); it is included for comparison of chatoyancies. R.V. Dietrich collection. (© photo by Dick Dietrich)

DESCRIPTION: Larvikite is the name applied widely to relatively coarse-grained anorthoclase-rich igneous rocks from the vicinity of Larvik, Norway. Anorthoclase (Na,K)AlSi₃O₈, which constitutes 90 or more per cent of most of these rocks, is , for all practical purposes, an intimate, submicroscopic intermixture of a plagioclase and an alkali feldspar. In petrographic circles this rock has been equated with both alkalic syenite and monzonite. Larvikite has the following properties:
    Color - light to dark bluish gray with two more-or-less distinct varieties -- one light bluish gray, the other dark bluish gray with golden brown overtones
     H. 6 - 6½
    S.G. ~2.59
    Light transmission - translucent (in thin pieces) to opaque
    Luster - overall pearly to subvitreous
    Miscellany - in essence larvikite is a light to dark gray coarse grained feldspar-rich grock that exhibits light blue "flashlike reflections" on some surfaces; the reflections, which come from individual anorthoclase grains that exhibit a chatoyant-like appearance, are frequently referred to as a pearl-gray iridescence, opalescence, or even labradorescence (in allusion to the appearance of labradorite -- see ANORTHOSITE entry).

OTHER NAMES: Larvikite has many trade names: Birds eye granite, Black moonstone, Blue Norwegian moonstone, Blue pearl granite, Blue granite, Blue antique, Blue pearl, Blue pearl fjord, Emerald pearl, "Labradorite," Larvik granite, Marina blue star, Norwegian pearl granite, Norwegian moonstone and Royal blue pearl granite are those I have seen. As is apparent, some of these name are unfortunate misnomers, particularly from the standpoint that terms like granite are included; certainly larvikite is not a granite in the laguage of petrography and it is hardly such in the usual sense of the word as used in the building/monument stone industry.

Along with the just mentioned names, my attention was recently directed to another name for larvikite -- one I cannot resist adding here: "Publich-houseite" (or "pub stone") is a nickname given larvikite in parts of Great Britain "because it is so common as a facing stone in British Pubs!" (www.bbc.co.uk/education)

Two chief variants of Larvikite are widely recognized because they direct attention to the overall color of those rocks. Personally, I -- and I have studied these rocks(!) -- fail to understand the basis of using the "emerald" designation. In any case, the two overall terms commonly applied are

Blue pearl -- the lighter colored variety (Figure A, left).
Emerald pearl - the darker colored variety (Figure A, right).

USES: The major use of larvikite is as an exterior and interior facing stone, and, indeed, it is a very popular one the world over. However, larvikite has also been fashioned for use as a gemstone and into several ornamental and functional items. Examples are: cabochons, free forms, and tumbled stones for pendants, brooches and other jewelry; paper weights and bookends; knobs for cabinet drawers and doors; eggs and spheres; and small carvings and relatively large sculptures.

OCCURRENCES: Relatively large masses, generally considered to be of igneous origin.

NOTEWORTHY LOCALITIES: Several active and abandoned quarries, each with its special variant of larvikite, are in the vicinity of Larvik, southern Norway.

Two other sources also seem noteworthy in that they have supplied larvikite used by lapidaries, and they serve as examples of commonly ignored sources of several rocks, including gemrocks :
1. The East Yorkshire “Boulder Committee” records the presence of "boulders" of Blue Pearl, Emerald Pearl and larvikite not otherwise characterized at more than a dozen localities in their domain. However, they clearly indicate that the larvikite boulders are among the "increasing number of human-influenced erratics on the coast ... [that represent] the use of exotic rocks for sea defences. These get broken up and washed along the coast by longshore drift, and soon ... become rounded and hard to distinguish from true glacial erratics. So we also record here the siting of these rocks so that future generations of geologists will be aware of this human interference.” (www.fortunecity.com)
2. James Small notes that "the only jewelry grade lapidary material which I have consistently found in that area is larvikite; a granite from Norway sometimes called "black moonstone", sometimes marketed as "labradorite"; definitely for sale in face polished pieces at tile shops as 'blue pearl'. The larvikite got to Lake Ontario as ballast in ocean-going ships which were used to transport grain to Europe either in the 1930s/late 1940s/ or both." (www.rockhounds.com) Unfortunately, I have been unable to contact Mr. Small from whom I had hoped I could get to see a specimen of the rock he describes and thus to verify his identification of the rock. So, I continue to wonder if what he reports as larvikite is anorthosite that was glacially transported (etc.) into the Lake Ontario area from one or more of the masses in Canada, or perhaps even from the Adirondacks of Northern New York, during the Pleistocene "Ice age." -- See Figure D and the possibly relevant comments under the Noteworthy Localities+ subheading in the ANORTHOSITE entry.

REMARKS: Larvikite (laurvikite) was named for the locality -- the La(u)rvik Fjord region, which is on the Skagerrak, approximately 100 km south of Oslo, Norway -- by Waldemar Christofer Brögger (1851-1940), Professor of Petrology at the University of Oslo.

A story about larvikite, which I have heard several people repeat but have been unable to verify, holds that larvikite first came on to the market as the result of a chance request made of the Norwegian group who were corresponding with the organizers of a World's Fair held in Germany in the early 1890s. According to that story, each country scheduled to have an exhibit or otherwise participate in the fair's activities was asked to send two of its decorative facing stones, to be judged by a panel of architects. Apparently at that time, Norway was only producing one facing stone, so the national committee -- not wanting to admit it -- asked Dr. Brögger to suggest a second rock that could be prepared and sent to the fair. Brögger is said to have answered, with no hesitation, that he thought the rock that winked at him in the moonlight as he rode in his buggy beside exposures along the La(u)rvik Fjord would be a good choice. So, a slab of this rock was prepared, transported, displayed at the fair AND voted the finest rock exhibited. -- True or not, La(u)rvikite has become a widely used decorative and facing stone during the last century plus, and today it can be seen here and there throughout the world.

Largely because of their overall color, grainsize or the presence or lack of preferred orientation of their component grains, some variants of larvikite have been found to be better suited for certain uses and ill-suited for other uses. Along this line, their trade names, given under the OTHER NAMES subheading, and statements about the different variants that are available from distributers are noteworthy.

As just mentioned, Larvikite can be seen as a facing stone on exterior and interior surfaces of buildings throughout the world. Examples range from its use in the United Nations building in New York City to counter tops in many private homes. One of my favorite uses, however, is the sculped so-to-speak modernistic bust of Thor Heyerdahl (1914-2002) of Kon-Tiki fame that is in Larvik. The setting, the form, and the use of larvikite all seem most appropriate considering the man and the fact that he was a native of Larvik.

Larvikite is described as "Norges nasjonalstein" (i.e., the national stone of N orway) in several recent publications (Børresen and Heldal, 2009). To date, I have not found if it has or has not been so-designated by any official act of the Norwegian government.

SIMULANTS:

Anorthosite - although some anorthosites resemble la(u)rvikite and could be used as simulates, I have found no evidence that any anorthosite has ever been represented as a substitute for la(u)rvikite used as a gemrock.

REFERENCE: Barth, 1944; Børresen and Heldal, 2009.

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