Lazulite

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Lazulite
Lazulite - Rapid Creek, Yukon (territory), Canada.jpg
Lazulite stage from Rapid Creek, Yukon, Canada
General and classification
other names

Blue path or blue path

chemical formula MgAl 2 (PO 4 ) 2 (OH) 2
Mineral class
(and possibly department) 		Phosphates, arsenates, vanadates
System no. to Strunz
and to Dana 		8.BB.40 ( 8th edition : VII / B.08)
41.10.01.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Room group (no.) (No. 14)
Lattice parameters a  = 7.144  Å ; b  = 7.278 Å; c  = 7.228 Å
β  = 120.51 °
Formula units Z  = 2
Physical Properties
Mohs hardness 5.5 to 6
Density (g / cm 3 ) 3.122 to 3.24
Cleavage indistinct
Break ; Tenacity shell-like to uneven
colour pale blue to black blue, blue-green, yellow-green
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.604 to 1.626
n β  = 1.626 to 1.654
n γ  = 1.637 to 1.663
Birefringence δ = 0.033 to 0.037
Optical character biaxial negative
Axis angle 2V = 61 to 70 °
Pleochroism strong: x = colorless; y = blue; z = dark blue

Lazulith , as Blauspat (h) or less often than Gersbyit or Klaprothin known is a rarely occurring mineral from the mineral class of the phosphates . It crystallizes in the monoclinic crystal system with the chemical composition MgAl 2 (PO 4 ) 2 (OH) 2 and develops mostly short prismatic or bipyramidal crystals , but also granular to massive mineral aggregates of pale blue to black-blue, blue-green or yellow-green color. Well-developed crystals are often transparent to translucent and have a glassy sheen on their surfaces.

Etymology and history

The name lazulite is derived from the Arabic word for sky and refers to the mineral's mostly blue color. It was first described in 1791 by JFW Widenmann and four years later by Martin Heinrich Klaproth .

The type locality is the Freßnitzgraben near Krieglach in Austria.

classification

In the old (8th edition) and new systematics of minerals according to Strunz (9th edition) , the lazulite belongs to the division of "anhydrous phosphates with foreign anions ". However, the new Strunz'sche mineral classification now subdivides more precisely according to the size of the cations and according to the molar ratio of the anions involved and the phosphate, arsenate or vanadate complex and the mineral is accordingly in the sub-section “With only medium-sized cations; (OH etc.): RO 4  ≥ 1: 1 "

The systematics of minerals according to Dana sorts the lazulite into the division of " anhydrous phosphates etc. with hydroxyl or halogen and the general formula (A 2+ B 2+ ) 3 (XO 4 ) 2 Z q ".

Education and Locations

Lazulite forms secondarily through hydrothermal processes from primary phosphate minerals in quartz veins or granite pegmatites . In addition to quartz, accompanying minerals are also andalusite , berylite , beryl , corundum , kyanite , muscovite , pyrophyllite , rutile and many others.

So far, lazulite has been found at 158 ​​locations, including Bundaberg and Mount Lofty Ranges (South Australia) in Australia; in the Bolivian departments of Cochabamba , La Paz and Potosí ; Bahia and Minas Gerais in Brazil; Copiapó in Chile; Fujian in China; Orivesi in Finland; Bavaria (Bavarian and Upper Palatinate Forest) and Thuringia (Thuringian Forest) in Germany; in some regions of Italy ; on Honshū in Japan; Yukon in Canada; at Antsirabe and Amoron'i Mania in Madagascar; Hedmark and Nordland in Norway; Hollenthon (Lower Austria), Raidlgraben and Hohe Tauern (Salzburg), Fischbach and Krieglach (Styria) in Austria; Gilgit (district) in Pakistan; at Torre de Moncorvo and Ferreira de Aves in Portugal; Gatumba in Rwanda; Eastern Siberia and Komi in Russia; Skåne , Värmland and Västergötland in Sweden; in the Swiss cantons of Graubünden and Valais ; Košice and Nitra in Slovakia; at Cadaqués in Spain; Bohemia in the Czech Republic; near Erdőbénye and Sopron in Hungary; as well as in many regions of the United States .

Crystal structure

Lazulite crystallizes in the monoclinic crystal system in the space group P 2 1 / c (space group no. 14) with the lattice parameters a  = 7.144  Å ; b  = 7.278 Å, c  = 7.228 Å and β = 120.51 ° as well as two formula units per unit cell .

See also

Individual evidence

  1. ↑ a b c Webmineral - Lazulite (English)
  2. ↑ a b American Mineralogist Crystal Structure Database - Lazulite (English, 1983)
  3. ↑ a b Lazulite at mindat.org (engl.)
  4. ↑ Mindat: Localities for Lazulite
  5. ↑ American Mineralogist Crystal Structure Database - Lazulite (English, 1983)

literature

Web links

Commons : Lazulite  - collection of images, videos and audio files