Mixit
| Mixit | |
|---|---|
 |
|
| General and classification | |
| chemical formula | BiCu 6 [(OH) 6 | (AsO 4 ) 3 ] • 3H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
08.DL.15 ( 8th edition : VII / D.53) 42.05.01.01 |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | hexagonal-dipyramidal 6 / m |
| Room group (no.) | P 6 3 / m (No. 176) |
| Lattice parameters | a = 13.64 Å ; c = 5.92 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 3 to 4 |
| Density (g / cm 3 ) | measured: 3.79 to 3.83; calculated: [4.04] |
| Cleavage | Please complete |
| Break ; Tenacity | uneven |
| colour | emerald green, blue green, light blue, light green, whitish |
| Line color | light bluish green |
| transparency | transparent to translucent |
| shine | Diamond gloss to silk gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.743 to 1.749 n ε = 1.810 to 1.830 |
| Birefringence | δ = 0.067 |
| Optical character | uniaxial positive |
| Pleochroism | visible: ω = colorless; ε = strong green |
Mixit is a rather seldom occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the hexagonal crystal system with the chemical composition BiCu 6 [(OH) 6 | (AsO 4 ) 3 ] • 3H 2 O, so chemically speaking it is a hydrous bismuth - copper - arsenate .
Mixit usually develops fibrous to needle-like crystals stretched along the c-axis in the form of radial, tufted mineral aggregates . Its color varies between emerald green, blue-green, light blue and light green color with light bluish-green stroke color .
With a Mohs hardness of 3 to 4, Mixite lies between the reference minerals calcite (3) and fluorite (4), so it is easier to scratch with a knife than fluorite. Undamaged crystal surfaces that are visible to the naked eye have a diamond-like sheen , while fine-grained aggregates have a silky shimmer .
Etymology and history
Mixit was first discovered in the "Geister-Gang" of the "Rovnost Mine" (Werner Mine) near Jáchymov in the Czech Republic and described in 1880 by Albrecht Schrauf (1837–1897), who named the mineral after its discoverer, the mining engineer Anton Mixa (1838–1906 ) named.
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the mixite belonged to the mineral class of "phosphates, arsenates and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 agardite (Ce) , Agardit- (Dy) , Agardit- (La) , Agardit- (Nd) , Agardit- (Y) , Calciopetersit , Goudeyit , Juanitait , Mrázekit , Petersit- (Y) and Zálesíit formed a distinct group.
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 Mixit to the class of “phosphates, arsenates and vanadates” and there to the department of “phosphates etc. with additional anions ; with H 2 O “. However, this section is further subdivided according to the size of the cations involved and the molar ratio of the other anions to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral is classified in the sub-section “With large and medium-sized cations; (OH etc.): RO 4 = 2: 1 "can be found where the" Mixit group "with the system no. 8.DL.15 and the other members agardite (Ce), agardite (La), agardite (Nd), agardite (Y), calciopetersite, goudeyite, petersite (Y), plumbo agardite and zálesíite.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the mixit to the class of "phosphates, arsenates and vanadates" and there to the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here he is also the namesake of the "Mixit group" with the system no. 42.05.01 and the other members Agardit- (Ce), Agardit- (Dy) , Agardit- (La), Agardit- (Nd), Agardit- (Y), Goudeyit, Plumboagardit and Zálesíit within the subdivision of " Aqueous Phosphates etc ., with hydroxyl or halogen with (A) 2 (XO 4 ) Z q × x (H 2 O) ”.
Education and Locations
Mixit forms as a secondary mineral in the oxidation zone of copper - deposits . Accompanying minerals include atelestite , barite , solid bismuth , bismuthite , erythrin , malachite and smaltite .
As a rather seldom occurring mineral formation, Mixit can sometimes be abundantly present at different sites, but overall it is not very common. So far (as of 2011) around 140 sites are known. In addition to its type locality Jáchymov, the mineral appeared in the Czech Republic in the area around Karlsbad and Schönfeld (Krásno), at Slavkovský štít and near Dubí and Krupka in the Ore Mountains.
In Germany, Mixit was found in many places in the Black Forest in Baden-Württemberg, including several mines near Wittichen and the well-known Clara mine near Oberwolfach. Furthermore, it was also at the Hartkoppe near Sailauf in Bavaria, near Gadernheim and Reichenbach in the Hessian municipality Lautertal , near Hasserode in Saxony-Anhalt, in several places in the area around Johanngeorgenstadt , Schneeberg and Schwarzenberg in the Saxon Ore Mountains, near Tirpersdorf and Mechelgrün in found in the community of Neuensalz in Vogtland in Saxony and near Ullersreuth in Thuringia Mixit.
In Switzerland, the mineral has so far only been discovered near Saint-Luc VS in the canton of Valais.
A well-known site is the ancient mining area around Lavrio in Greece, where beautiful aggregates with tufted mixite crystals were found.
Other sites are in Argentina, Australia, Chile, France, Italy, Japan, Mexico, Namibia, Poland, Spain, England and Scotland in the United Kingdom (Great Britain) and Arizona, Colorado, California, Nevada, New Mexico and Utah in the United States (USA).
Crystal structure
Mixit crystallizes isotypically with agardite in the hexagonal crystal system in the space group P 6 3 / m (space group no. 176) with the lattice parameters a = 13.64 Å and c = 5.92 Å ( c / a = 0.434) and 2 formula units per Unit cell .
Mixit and the end members of the agardite series form a continuous mixed crystal series , the individual members of which differ based on the metal cations they contain. In case of doubt, an exact determination is only possible by means of crystal structure analyzes.
See also
literature
- A. Schrauf: Mixit, a new copper bismuth hydroarsenate (PDF; 455 kB), in: P. Groth (Hrsg.): Zeitschrift für Krystallographie und Mineralogie , Volume 4, Leipzig 1880, pp. 277-281
- Kurt Walenta (1960): Chlorotil and Mixit , in: New year book for mineralogy , monthly books: pp. 223–236
- K. Mereiter, A. Preisinger (1986): Crystal structure data of the bismuth minerals Atelestit, Mixit, and Pucherit , in: Anzeiger der Österreichische Akademie der Wissenschaften , Mathematisch-Naturwissenschaftliche Klasse, Anzeiger: 123: P. 79-81
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 189 ( Dörfler Natur ).
Web links
- Mineral Atlas: Mixit (Wiki)
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 517 .
- ↑ Webmineral - Mixite (English)
- ↑ a b c Handbook of Mineralogy - Mixite (English, PDF 63.6 kB)
- ↑ a b c d Mixite at mindat.org (engl.)
- ↑ Schrauf Albrecht. In: Austrian Biographical Lexicon 1815–1950 (ÖBL). Volume 11, Verlag der Österreichischen Akademie der Wissenschaften, Vienna 1999, ISBN 3-7001-2803-7 , p. 181.
- ↑ Mindat - Number of locations at mindat.org
- ^ Paul Ramdohr , Hugo Strunz : Klockmanns textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, Stuttgart 1978, ISBN 3-432-82986-8 , p. 653 .