Zairit
| Zairit | |
|---|---|
 Field of view 6 mm |
|
| General and classification | |
| other names |
|
| chemical formula | BiFe 3+ 3 [(OH) 6 | (PO 4 ) 2 ] |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8th BL.13 ( 8th edition : VII / B.36) 05.41.12.03 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | ditrigonal-scalenohedral; 3 2 / m |
| Space group | R 3 m (No. 166) |
| Lattice parameters | a = 7.02 Å ; c = 16.37 Å |
| Formula units | Z = 3 |
| Physical Properties | |
| Mohs hardness | 4.5 |
| Density (g / cm 3 ) | measured: 4.37 (5); calculated: 4.42 (3) |
| Cleavage | Please complete |
| colour | greenish white, yellowish green |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss, resin or wax gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.820 to 1.830 n ε = 1.810 |
| Birefringence | δ = 0.010 to 0.020 |
| Optical character | uniaxial negative |
Zaïrit is a very rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates". It crystallizes in the trigonal crystal system with the chemical composition BiFe 3+ 3 [(OH) 6 | (PO 4 ) 2 ] and is thus a bismuth - iron - phosphate with additional hydroxide .
Since iron can be replaced ( substituted ) by small amounts of aluminum in naturally occurring zaïrit samples , the formula is also given in various sources as Bi (Fe 3+ , Al) 3 [(OH) 6 | (PO 4 ) 2 ].
Zaïrit is usually found in the form of coarse mineral aggregates with a wax-like sheen on the surfaces. In its pure form, Zaïrit is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also appear white and, due to foreign admixtures, take on a greenish-white to yellowish-green color, the transparency decreasing accordingly.
Etymology and history
Zaïrit was first discovered in the Eta-Etu district in the Kivu region of the Democratic Republic of the Congo and described in 1975 by Léopold Van Wambeke . The French name of the Democratic Republic of the Congo state where Van Wambeke found the mineral was Zaïre at the time .
Type material of the mineral is kept in the Royal Museum for Central Africa in Tervuren, Belgium (catalog no. RMG14065).
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the zaïrit belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates, with foreign anions F, Cl, O, OH", where together with arsenoflorencit- (Ce) , arsenoflorencit- (La) , arsenoflorencit- (Nd) , arsenocrandallite , arsenogorceixite , arsenogoyacite , arsenowaylandite , benauite , crandallite , dussertite , eylettersite , florencite- (Ce) , florencite- (La) , Florencit- (Nd) , Gorceixit , Goyazit , Graulichit- (Ce) , Kintoreit , Pattersonit , Philipsbornit , Plumbogummit , Segnitit , Springcreekit and Waylandite the "Crandallit group" with the system number. VII / B.36 .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns the zaïrit to the category of “phosphates etc. with additional anions; without H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the additional anions to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With medium-sized and large cations; (OH etc.): RO 4 = 3: 1 “can be found where it is found together with arsenoflorencite (Ce), arsenoflorencite (La), arsenoflorencite (Nd), eylettersite, florencite (Ce), florencite ( La), Florencit- (Nd), Graulichit- (Ce) and Waylandite form the unnamed group 8.BL.13 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Zaïrit to the class of "phosphates, arsenates and vanadates" and there in the category of "anhydrous phosphates etc., with hydroxyl or halogen". Here it can be found together with arsenogorceixite, eylettersite and waylandite in the “ waylandite group ” on May 41, 2012 within the subdivision “ anhydrous phosphates etc., with hydroxyl or halogen with (AB) 2 (XO 4 ) Z q ”.
Crystal structure
Zaïrit crystallizes isotypically with crandallite in the trigonal crystal system in the space group R 3 m (space group no. 166) with the lattice parameters a = 7.02 Å and c = 16.37 Å and 3 formula units per unit cell .
Education and Locations
Zaïrite formed in the weathering zone of quartz - wolframite - deposits , where he next quartz, among others, still with native bismuth , the bismuth Bismutit and various micas socialized occurs.
Apart from its type locality in the Eta-Etu (Kivu) district in the Democratic Republic of the Congo, the mineral has so far (as of 2014) only been found in Germany on the Kreuzberg in Pleystein , a rose quartz rock in Pleystein in the Upper Palatinate district of Neustadt an der Waldnaab .
See also
literature
- L. Van Wambeke: La zairite, un nouveau mineral appartenant a la serie de la crandallite . In: Bulletin de la Societe franyaise de Mineralogie et de Cristallographie . tape 98 , 1975, pp. 351–353 ( rruff.info [PDF; 178 kB ; accessed on January 14, 2018]).
Web links
- Mineral Atlas: Zaïrit (Wiki)
Individual evidence
- ↑ IMA / CNMNC List of Mineral Names, September 2014 (PDF 1.5 MB, p. 193)
- ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p. 808 .
- ↑ a b c d Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 463 .
- ↑ a b c Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 635 (first edition: 1891).
- ↑ a b c Zaïrite . 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; 61 kB ; accessed on January 14, 2018]).
- ↑ a b Webmineral - Zaïrite
- ↑ a b Mindat - Zaïrite
- ↑ Les Mineraux de la Republique Democratique du Congo at euromin.w3sites.net ( memento of the original from October 29, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Royal Museum for Central Africa - database entry of the Zaïrit type material
- ↑ Find location list for Zaïrit in the Mineralienatlas and in Mindat
