Leucophosphite

from Wikipedia, the free encyclopedia
Leucophosphite
Hureaulite-Leucophosphite-sea73c.jpg
Leucophosphite in paragenesis with hureaulite
General and classification
chemical formula KFe 3+ 2 [(PO 4 ) 2 | OH] • 2H 2 O
Mineral class
(and possibly department) 		Phosphates, arsenates and vanadates
System no. to Strunz
and to Dana 		8.DH.10 ( 8th edition : VII / D.27)
11/22/06/01
Crystallographic Data
Crystal system Monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / n (No. 14, position 2)Template: room group / 14.2
Lattice parameters a  = 9.782  Å ; b  = 9.658 Å; c  = 9.751 Å
β  = 102.24 °
Formula units Z  = 4
Physical Properties
Mohs hardness 3.5
Density (g / cm 3 ) measured: 2.948; calculated: 2.911
Cleavage Completely at {100}
colour white, yellow-brown, orange-brown, pink, green-brown, brownish purple
Line color White
transparency translucent
shine Glass gloss to wax gloss
Crystal optics
Refractive indices n α  = 1.707
n β  = 1.721
n γ  = 1.739
Birefringence δ = 0.032
Optical character biaxial positive
Axis angle 2V = calculated: 84 °
Other properties
Chemical behavior Very good in acids

Leocophosphite is a rare mineral from the mineral class of phosphates , arsenates and vanadates . It crystallizes in the monoclinic crystal system with the chemical composition KFe 3+ 2 [(PO 4 ) 2 | OH] · 2H 2 O. It is therefore a potassium - iron phosphate with additional hydroxide ions , which contains water of crystallization .

It forms diamond-like, 1 cm large crystals , but also fine-grained, chalk-like, sometimes amorphous masses. The mineral has a brown color, which can have different colored influences in different forms. Leucophosphite is translucent with refractive indices between 1.70 and 1.74.

With a Mohs hardness of 3.5, it is one of the soft minerals.

Etymology and history

Leucophosphite was first described by ES Simpson in 1931. He discovered it during an investigation on a rock with a high concentration of phosphate and named it after leukos (Gr. For white ) and phosphoros (English for phosphorus ). After the investigation, which was carried out in comparison to Variscite (Fe 3+ [PO 4 ] · 2H 2 O, at that time also sometimes called Redonite ), he established the formula of the new mineral with K 2 (Fe, Al) 7 (OH) 11 (PO 4 ) 4 · 6H 2 O solid. His test results indicated the following mixing ratio:

Al 2 O 3 12.5% Fe 2 O 3 32.82% Cr 2 O 3 in traces
FeO in traces MnO 0.22% MgO 0.73%
(NH 4 ) 2 O 0.09% Na 2 O 0.13% K 2 O 7.88%
H 2 O (+) 12.28% P 2 O 5 26.29% CO 2 0.17%
SiO 2 in traces TiO 2 in traces H 2 O (-) 6.59%

In a new chemical analysis in 1952, JM Axelrod, Maxwell K. Carron, Charles Milton and TP Thayer came up with the formula K 2 [Fe 3+ 4 (OH) 2 (H 2 O) 2 (PO 4 ) 4 ] · 2H 2 O. The formula is still valid today in its simplified form KFe 3+ 2 [(PO 4 ) 2 | OH] · 2H 2 O.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the leukophosphite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates with foreign anions", where together with minyulite , spheniscidite and Tinsleyit named after him Leucophsophit group with the system number VII / D.27 formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also assigns leukophosphite to the category of “phosphates etc. with additional anions; with H 2 O “. However, this is further subdivided according to the size of the cations and the amount of other anions, so that the mineral is classified in the sub-section “With large and medium-sized cations; (OH etc.): RO 4  <1: 1 “can be found, where it is with spheniscidite and tinsleyite in the leukophosphite group with the system number 8.DH.10 also named after him .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns leukophosphite to the class of "phosphates, arsenates and vanadates" and there in the section "water-containing phosphates etc., with hydroxyl or halogen" (no. 42) and there in the subgroup “Water-containing phosphates etc., with hydroxyl or halogen with (AB) 4 (XO 4 ) 3 Zq × x (H 2 O)”. Here it can also be found together with spheniscidite and tinsleyite of the unnamed group with the system number 42.11.06 .

Crystal structure

Leucophosphite crystallizes monoclinically in the space group P 2 1 / n (space group no. 14, position 2) with the lattice parameters a  = 9.782  Å , b  = 9.658 Å, c  = 9.751 Å and ß  = 102.24 ° as well as four formula units per unit cell . Template: room group / 14.2

The crystal water molecules are located in larger cavities in the crystal structure. The phosphate anions ([PO 4 ] 3− ) form tetrahedra .

Education and Locations

Leucophosphite is formed by the reaction of guano with iron-containing minerals. It also arises from hydrothermal transformations of iron phosphates in pegmatite rocks or by replacing fossil wood . It is communalized with variscite, strictite , phosphosiderite , cyrilovite , manganese-containing lipscombite , frondelite , vivianite , diadochite , ferrostrunzite , fluorapatite , rockbridgeite and triphyline .

About 100 sites of leukophosphite are known.

In Germany there are only sites in Bavaria . In the Upper Palatinate there is a place of discovery near Pleystein and Hagendorf , municipality Waidhaus . There is also a site in Althütte , municipality of Waldmünchen . In the district of Lower Bavaria there is a site in Bodenmais , in the district of Upper Franconia there is a site in Leupoldsdorf .

Other European sites can be found in the French regions of Auvergne-Rhône-Alpes , Bretagne , Nouvelle-Aquitaine and Occitania , in the Portuguese districts of Guarda and Viseu , in the Romanian region of Hunedoara , in the Spanish autonomous community of Castile and León , in the Czech regions Bohemia and Moravia, as well as England and Scotland in the United Kingdom .

There are also sites in Antarctica , Argentina , Australia , Brazil , Chile , Libya , Madagascar , Malaysia , Mexico , Morocco , Namibia , Rwanda , South Africa and the US states of Alabama , Arizona , California , Colorado , Indiana , Maine , Nevada , New Hampshire , New Mexico , North Carolina , South Dakota , Virginia, and Wisconsin .

See also

literature

  • JM Axelrod, MK Carron, C. Milton, TP Thayer: Phosphate mineralization at bomi hill and bambuta, liberia, west africa . In: American Mineralogist . tape 37 (November / December edition), 1952, p. 883-909 ( PDF ).
  • Marie Louise Lindberg: Leucophosphite from the sapucaia pegmatite mine, minas gerais, brazil . In: American Mineralogist . tape 42 (January / February edition), 1957, p. 214-221 ( PDF ).
  • MJ Wilson, DC Bain: Occurrence of leucophosphite ina soil from Elephant Island, British Antarctic Territory . In: American Mineralogist . tape 1 , 1976, p. 1027-1028 ( PDF ).

Web links

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

Individual evidence

  1. ↑ a b c d e f g Leucophosphite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy . Mineralogical Society of America, 2001 ( PDF ).
  2. ↑ a b c Mindat - Leucophosphite (English)
  3. ↑ a b Mineralienatlas: Leukophosphit
  4. ^ ES Simpson: Contributions to the mineralogy of Western Australia: Variscite (renardite) and leucophosphite (Sp. Nov.), Ninghanboun hills, SW In: Journal of the Royal Society of Western Australia . tape 18 , 1932 ( PDF ).
  5. ↑ Paul Brian Moore: Octahedral tetramer in the crystal structure of leucophosphite, K 2 [Fe 3+ 4 (OH) 2 (H 2 O) 2 (PO 4 ) 4 ] · 2H 2 O . In: American Mineralogist . tape 57 , 1972 ( PDF ).
  6. ↑ The New IMA List of Minerals (as of December 2014)
  7. ↑ a b c d List of locations where leukophosphite is found in the Mineralienatlas and Mindat