from Wikipedia, the free encyclopedia
Labradoryt, Madagascar.JPG
General and classification
chemical formula (Ca, Na) Al (Si, Al) 3 O 8
Mineral class
(and possibly department)
Tectosilicates ; Feldspar group (anorthoclase-anorthite-banalsite series)
System no. to Strunz
and to Dana
9.FA.35 ( 8th edition : VIII / F.03c)
Similar minerals Andesine
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Physical Properties
Mohs hardness 6 to 6.5
Density (g / cm 3 ) 2.8
Cleavage perfect according to (001), good according to (010)
Break ; Tenacity uneven to scalloped
colour colorless, white to dark gray, green
Line color White
transparency transparent to translucent
shine Glass gloss to matt
Crystal optics
Optical character biaxial positive
Pleochroism colorless
Other properties
Chemical behavior decomposes in acids, can be melted with a soldering iron
Special features shiny metallic play of colors, called labradorescence

Like andesine, labradorite is no longer an independent mineral , but is a plagioclase , a relatively common mineral mixture of albite and anorthite from the group of feldspars and the mineral class of silicates . Its anorthite content is by definition 50 to 70% (An 50-70 ).

Special properties

Detail view of a polished labradorite

What is striking about labradorite is the iridescent play of colors in a metallic sheen, the so-called labradorescence (verb:  labradorize ), which is caused by interference and reflection of the light on the submicroscopic segregation lamellae . This shimmer is predominantly blue, purple and green, but can occasionally also be found in other colors.

Etymology and history

Labradorite was named after its first location, the Labrador Peninsula . The Czech missionary Father Adolf discovered him on the coast in 1770 .

Spectrolite was first described in 1896 in the book Edelsteinkunde by Max Bauer . However, it got its name from the Finnish professor Aarne Laitakari because of its iridescence in all spectral colors .


Typical spectrolites from Ylämaa, Finland

As Spektrolith a labradorite from is Ylämaa called in Finland, which is characterized by the full color spectrum of Labradoreszenz.

Madagascar moonstone or rainbow moonstone , on the other hand, is the trade name for a white, almost transparent labradorite with a strong blue surface shimmer, which is often used as an imitation for the real moonstone .

Education and Locations

Labradorite forms either magmatically in dunite , gabbros , basalt and anorthosite or metamorphically in amphibolite .

Important sites are Québec and Nain in Labrador / Canada , the Korostanskiymassiv in Ukraine , Ylämaa in Finland , the area around Larvik in Norway and Madagascar .

Use as a gem stone

Tobacco box made of gold with inlaid labradorites

Due to its beautiful shimmer, labradorite is often used to make gemstones and craft objects. However, its high sensitivity to any influence of heat, acids and alkalis as well as galvanic baths make processing difficult. Even cleaning in an ultrasonic bath damages the stone. In addition, labradorite is softer than quartz and therefore sensitive to scratches from the ubiquitous dust , which mostly also contains fine quartz grains, which over time makes the surface of the stone appear dull. This is especially true for mineral floor coverings that contain labradorite.

See also


  • Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Villager Nature ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 266 .
  • Martin Okrusch, Siegfried Matthes: Mineralogy. An introduction to special mineralogy, petrology and geology . 7th, completely revised and updated edition. Springer, Berlin [a. a.] 2005, ISBN 3-540-23812-3 , pp. 123 .
  • Nils Nordenskjöld: Investigation of some new phenomena in the play of colors in the Labrador . In: Annals of Physics and Chemistry . 19, second piece, 1830, p. 179–190 ( limited preview in Google Book Search).

Web links

Commons : Labradorite  - collection of images, videos and audio files
Wiktionary: Labradorite  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. Mineral encyclopedia: Labradorite ( Memento of the original from March 13, 2007 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  2. ^ A b Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 182 .
  3. Bernhard brother embellished stones. Recognizing imitations and manipulations in gemstones and minerals . Neue Erde, Saarbrücken 2005, ISBN 3-89060-079-4 , p. 82 .