Labrador - named after the Labrador Peninsula ( Canada ), where it was first found in 1770 [1] .
| Labrador | |
|---|---|
 Labrador from Madagascar | |
| Formula | 30–50% NaAlSi 3 O 8 + 50–70% CaAl 2 Si 2 O 8 |
| Impurity | Fe, K, Mg |
| Physical properties | |
| Color | Smoky gray, dark gray to almost black with a vibrant play of colors |
| Trait color | White |
| Shine | Glass to metal |
| Transparency | Opaque |
| Hardness | 6-6.5 |
| Cleavage | Perfect |
| Kink | Uneven, stepped; fragile |
| Density | 2.69—2.70 g / cm³ |
| Syngonia | Triclinic |
| Refractive index | 1,560-1,568 |
In some languages, it is also called labradorite ( English Labradorite ), which can lead to confusion with the rock labradorite . Sometimes the terms sysyak, lynx eye, tavusit or iris are also used as a synonym [2] .
Content
- 1 Properties
- 2 Deposits
- 3 Varieties
- 4 Application
- 5 notes
- 6 Literature
- 7 References
Properties
A member of the isomorphic series of NaAlSi 3 O 8 ( albite ) - CaAl 2 Si 2 O 8 ( anorthite ), contains 50–70% of the anorthite component [1] .
Crystals (tabular) are rare, more often found in the form of dense coarse-grained aggregates and perforated inclusions. It is formed in intrusive rocks of the main composition.
Composition (%): Na 2 O - 3.96; CaO - 10.93; Al 2 O 3 - 26.83; SiO 2 55.49. Impurities: Fe 2 O 3 (1.6%), K 2 O (0.36%), H 2 O (0.51%), MgO (0.15%).
Birefringence +0.008. Pleochroism and variance are absent. The absorption spectrum is not interpreted; luminescence is usually not.
The labrador is characterized by bright rainbow ebbs (flares), called irisation (or labradorization, or labradorescence). Most often, these tints have blue and blue hues, but can be green, yellow and red. This effect is associated with the interference of light in thin plates of different compositions, of which the mineral consists.
Crumbles upon squeezing, easily splits upon impact. It is melting . It is soluble in acids .
Deposits
Labrador is found in Canada ( Labrador Peninsula, Newfoundland Island), Mexico , USA , Brazil , Madagascar , Ukraine ( Volyn , Zhytomyr Region ), in Fennoscandia (especially in Finland ), Australia ( New South Wales ), India .
Varieties
Depending on the crystallographic and optical properties, the following varieties of labrador are distinguished:
- Spectrolite is a labrador that casts with all the colors of the rainbow. Spectrolites are found in Finland, where they were discovered in 1940 in Juliaa during the construction of the Salpa Line (line of fortifications); The development of spectrolytes in Juliaa began after the Second World War .
- Black moonstone - a labrador with blue and blue irises (the central staircase of the RSL - “Leninki” is trimmed with such a labrador, the rounded blue spots, cast with mother-of-pearl, become clearly visible under appropriate lighting, natural sunlight falling from the windows)
- (simply called “moonstone” is usually called adular - a mineral with light blue iris) [1] .
- Sunstone is a golden iris labrador mined in Oregon (USA) [1] .
Application
Since the end of the 18th century it has been a valuable jewelry and ornamental stone . It is also used as a facing stone (for example, it is used in the decoration of the Lenin Mausoleum ).
On the polished surface, irisation is clearly manifested, therefore, spectrolytes are used for the manufacture of jewelry and crafts.
Madagascar labradorites with a strong blue tint are also appreciated. Australian colorless, tan transparent labradorites are successfully faceted .
Notes
- ↑ 1 2 3 4 Minerals. Treasures of the Earth, 2013 .
- ↑ B. F. Kulikov, V. V. Bukanov Dictionary of gem stones, Leningrad, "Nedra", 1988, p. 58
Literature
- Nordenskiöld N. Untersuchung einiger neuer Phänomene beim Farbenspiel des Labradors // Annalen der Physik und Chemie. 1830. Vol. 95. S. 179-190.
- Schumann V. The world of stone. Precious and ornamental stones. - M.: Mir, 1986 .-- S. 158.
- Labrador // Minerals. Treasures of the Earth: Journal. - 2013. - No. 3. - 200,000 copies. - ISSN 2075-0587 .