Cryolithionite

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Cryolithionite
General and classification
chemical formula Na 3 Al 2 3+ Li 3 F 12
Mineral class
(and possibly department) 		Halides
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Ia 3 d (No. 230)Template: room group / 230
Lattice parameters a  = 12.122  Å
Formula units Z  = 8
Frequent crystal faces Rhombic dodecahedron {110}
Physical Properties
Mohs hardness 2.5 - 3
Density (g / cm 3 ) measured: 2.777-2.778 calculated: 2.771
Cleavage clearly after {110}
colour fallowless
Line color White
transparency transparent
shine Glass gloss
Crystal optics
Refractive index n  = 1.3395
Birefringence δ = -
Other properties
Chemical behavior somewhat soluble in water

The mineral cryolite ionite is a very rare fluoride from the upper group of garnets with the composition Na 3 Al 2 Li 3 F 12 . It crystallizes in the cubic crystal system with the structure of garnet. The rhombic dodecahedral crystals are colorless and transparent and reach a size of up to 17 cm.

Cryolite ionite is found in fluorine- and lithium- rich pegmatites . Apart from its type locality , the Ivigtut cryolite deposit in Greenland , cryolite ionite has so far only been found in small quantities in a few other places in the world.

Etymology and history

Cryolite ionite was discovered in the spring of 1903 in the cryolite deposit near Ivittuut on the Arsukfjord in Kommuneqarfik Sermersooq , Greenland by the mining engineer ME-F. Edwards. Niels Viggo Ussing described the new mineral and named it for its resemblance to cryolite and its high lithium content Kryolithionit . He also pointed out the relationship with garnet.

Georg Menzer clarified the structure in Berlin in 1927 and confirmed the structural relationship between cryolithionite and garnet. Another structural investigation in 1971 by S. Geller confirmed Menzer's results.

classification

The current classification of the International Mineralogical Association (IMA) counts the cryolite ionite in the garnet upper group, where so far (2013) it is the only mineral with 3 positive charges (Li 3 ) on the tetrahedrally coordinated lattice position.

In the 8th edition of the mineral systematics according to Strunz , which is now outdated but still in use , cryolite ionite belonged to the mineral class of "halides", where it was classified as [BF 4 ] 1− , [SiF 6 ] 2− and [AlF 6 ] 3− together with Bøgvadit , Calcjarlit , Colquiriit , Elpasolite , Jarlit , Jørgensenit , Kryolite , Simmonsit the group of the cryolite-elpasolite group with the system no. III / B.03 forms.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001, also assigns cryolithionite to the class of "halides". There it is classified according to its composition and structure in department C (complex halides) in subdivision B. Island aluminofluorides (Neso aluminofluorides) as a single mineral with system no. 3.CB.05 led.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the cryolite ionite to the “halide” class and there to division 11.06 (complex halides - aluminum fluorides with various formulas). Here it is used as a single mineral with system no. 06/11/04/01 .

Crystal structure

Cryolite ionite crystallizes with cubic symmetry in space group Ia 3 d (space group no. 230) and the lattice parameter a  = 12.122  Å as well as 8 formula units per unit cell . Template: room group / 230

The structure is that of garnet . Sodium (Na + ) occupies the dodecahedral X-position surrounded by 8 oxygen, aluminum (Al 3+ ) the octahedral Y-position surrounded by 6 oxygen and lithium (Li + ) the tetrahedral Z-position surrounded by 4 oxygen.

Education and Locations

Cryolite ionite forms in the late phase of the crystallization of fluorine- and lithium- rich pegmatites. At its type locality , the cryolite deposit near Ivittuut on the Arsukfjord in Kommuneqarfik Sermersooq , Greenland , it was found in the form of cm- to dm-sized crystals enclosed in cryolite. Cryolite and cryolite ionite occur here together with quartz , fluorite and siderite .

In the Gasberg Topas cryolite mine near Miass in the Ilmen Mountains, Chelyabinsk Oblast in the southern Urals , Russia , graphical adhesions of cryolite and cryolite ionite were found in a one-meter druse of a granite pegmatite. At the contact with the granite, cryolite ionite occurred together with chiolite and fluorite .

In the Zapot pegmatite near Hawthorne in Mineral County (Nevada) , Nevada , USA , massive, fine crystalline adhesions of cryolite ionite with cryolite, simmensonite and traces of elpasolite and topaz occur. This primary paragenesis was partially converted into pachnolite , weberite , prosopite , ralstonite , fluorite and a second generation cryolite ionite.

Furthermore, the mineral could so far (as of 2017) only be detected in another pegmatite in the southern Urals (Suran deposit) and in an outcrop of brownish-yellow weathering products near Rio Verde in San Luis Potosí , Mexico .

See also

Web links

Individual evidence

  1. ↑ a b c d e f g h i j k NV Ussing: Sur la cryolithionite, espèce minérale nouvelle . In: Oversigt over det Kongelige Danske Videnskabernes Selskabs Forhandlinger . No. 1 , 1904, p. 2–12 ( rruff.info [PDF; 312 kB ; accessed on May 16, 2017]).
  2. ^ A b c d e S. Geller: Refinement of the crystal structure of cryolithionite . In: American Mineralogist . tape 56 , no. 1 , February 1971, p. 18–23 ( rruff.info [PDF; 270 kB ; accessed on May 16, 2017]).
  3. ↑ Hans Pauly: Cryolite, chiolite and cryolithionite: optical data redetermined. In: Bulletin of the Geological Society of Denmark . tape 26 , 1977, pp. 95-101 ( 2dgf.dk [PDF; 632 kB ; accessed on May 16, 2017]).
  4. ↑ a b List of locations where cryolithionite was found in the Mineralienatlas and Mindat
  5. ↑ Cryolithionite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 68  kB ; accessed on May 16, 2017]).
  6. ^ JC Bailey: Formation of cryolite and other aluminofluorides: A petrologic review. In: Bulletin of the Geological Society of Denmark . tape 29 , 1980, pp. 1-45 ( psu.edu [PDF; 3.3 MB ; accessed on May 16, 2017]).
  7. ↑ Eugene E. Foord, Joseph T. O'Connor, John M. Hughes, Stephen J. Sutley, Alexander U. Falster, Arthur E. Soregaroli, Frederick E. Lichte and Daniel E. Kile: Simmonsite, Na 2 LiAlF 6 , a new mineral from the Zapot amazonite-topaz-zinnwaldite pegmatite, Hawthorne, Nevada, USA In: American Mineralogist . tape 84 , 1999, pp. 769–772 ( minsocam.org [PDF; 277 kB ; accessed on May 16, 2017]).