Labradorite
| Labradorite | |
|---|---|
 |
|
| 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) 76.01.03.04 |
| 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
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 .
Varieties
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
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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
literature
- 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
- Mineral Atlas: Labradorite and Spectrolite (Wiki)
- Uni-Tübingen: mineral properties; Color of minerals; III. Pseudochromatic coloration (for labradorite)
- Mineral Lexicon - Labradorite
- Gem Etiquette - Labradorite
- Mindat - Labradorite (English)
- Webmineral - Labradorite (English)
Individual evidence
- ↑ 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.
- ^ 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 .
- ↑ Bernhard brother embellished stones. Recognizing imitations and manipulations in gemstones and minerals . Neue Erde, Saarbrücken 2005, ISBN 3-89060-079-4 , p. 82 .
