Descloicit
| Descloicit | |
|---|---|
 |
|
| General and classification | |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates, vanadates |
|
System no. to Strunz and to Dana |
8.BH.40 ( 8th edition : VII / B.27) 05.41.02.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-dipyramidal; 2 / m 2 / m 2 / m |
| Space group | Pnam (No. 62, position 6) |
| Lattice parameters | a = 7.59 Å ; b = 9.42 Å; c = 6.06 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | {100}, {010}, {110}, {120} |
| Physical Properties | |
| Mohs hardness | 3 to 3.5 |
| Density (g / cm 3 ) | measured: ≈ 6.2; calculated: 6.202 |
| Cleavage | no |
| Break ; Tenacity | shell-like to uneven; brittle |
| colour | light to dark brown, olive green, gray to black, black green; with increasing copper content from yellow to orange |
| Line color | light yellow brown |
| transparency | transparent to opaque |
| shine | Fat luster, diamond luster |
| Crystal optics | |
| Refractive indices |
n α = 2.185 n β = 2.265 n γ = 2.350 |
| Birefringence | δ = 0.165 |
| Optical character | biaxial negative |
| Axis angle | 2V = measured: 85 to 90 °; calculated: 88 ° |
| Other properties | |
| Chemical behavior | easily soluble in acids |
| Special features | easily meltable |
Descloizit is a rather seldom occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the idealized chemical composition PbZn [OH | VO 4 ] and is thus chemically a basic lead - zinc vanadate.
Descloizit is the zinc analogue of mottramite (PbCu [OH | VO 4 ]) and forms a complete mixed crystal row with it . In natural descloiccy, a small amount of zinc is therefore usually replaced ( substituted ) by copper , which is expressed in the formula with element symbols in round brackets: Pb (Zn, Cu) [OH | VO 4 ]. In any mixing ratio, orthorhombic crystals with similar crystallographic and physical properties are formed. However, the color changes more and more into a brownish, almost black red, the higher the zinc content becomes. In the copper-rich Mottramit, on the other hand, the color is green to black-green.
The mineral develops mainly prismatic, columnar or tabular crystals , but is also found in the form of radial or grape mineral aggregates and crusty coatings.
Etymology and history
Descloizit was first discovered in the Sierras de Córdoba in the central Argentine province of Córdoba . The mineral was described in 1854 by Augustin Alexis Damour (1808-1902), who named the mineral after his colleague and friend, the French mineralogist Alfred Des Cloizeaux (1817-1897), in honor of his services in the field of crystallography.
classification
In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the Descloizit 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 he together with Arsendescloizit , Čechit , Mottramit and Pyrobelonit the "Descloizitgruppe" with the system no. VII / B.27 .
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 Descloizit 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 (OH etc.) to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With medium-sized and mostly large cations; (OH etc.): RO 4 = 1: 1 ”can be found, where the“ Descloizitgruppe ”with the system no. 8.BH.40 and the other members Čechit, Mottramit and Pyrobelonit.
The systematics of minerals according to Dana also assigns the descloicit to the class of "phosphates, arsenates and vanadates" and there in the department of "anhydrous phosphates etc., with hydroxyl or halogen". Here he is also the namesake of the "Descloizitgruppe" with the system no. 41.05.02 and the other members Mottramit, Pyrobelonit, Čechit and Duftit-Alpha can be found in the subsection " Anhydrous phosphates etc., with hydroxyl or halogen with (AB) 2 (XO 4 ) Z q ".
Crystal structure
Descloizit crystallizes orthorhombically in the space group Pnam (space group no. 62, position 6) with the lattice parameters a = 7.59 Å ; b = 9.42 Å; c = 6.06 Å and 4 formula units per unit cell .
Modifications and varieties
The green varieties of Descloizit are called psittacinite .
Education and Locations
Descloizit is a typical secondary mineral and is found in the oxidation zone of ore veins, especially in some lead-zinc-copper ore deposits.
As a rather rare mineral formation, Descloizit can sometimes be abundant at various sites, but overall it is not very common. Worldwide, around 340 sites are known to date (as of 2017). In addition to its type locality Sierras de Córdoba, the mineral was also found in Argentina in the nearby Venus mine and at La Plata in the Punilla department and in the El Guaico district in the Minas department in the Córdoba province . It was also found in the Gonzalito lead mine about 48 km north of the Sierra Grande and in the Blanquita quarry near Los Menucos in the Río Negro province and in the Mina Diana in the La Poma department .
In Germany, Descloizit was found in various tunnels and spoil heaps near Hofsgrund , in the St. Benedikt mine near the Katzensteig part of the municipality , the Clara mine near Oberwolfach and the St. Caroli mine near Zähringen in the Black Forest (Baden-Württemberg); on the Königsbergalpe on Jenner , in the lead mine on Riedbodeneck near Mittenwald and in the Ewiggangrevier near Kienberg in Upper Bavaria and in the Krennbruch near Saldenburg in Lower Bavaria; at two sites on Borstein and Hohenstein near Reichenbach (Lautertal) in Hesse; in the Ferdinande mines near Flandersbach and Eisenberg near Velbert in North Rhine-Westphalia ; in the Johanna mine near Bobenthal in Rhineland-Palatinate; on the Grubenberg near Walhausen in Saarland and in the Yellow Birch Pit at the Schwarzenberg Dome near Schwarzenberg / Erzgeb. in the Saxon Ore Mountains .
In Austria, the mineral has so far mainly appeared in the regions of Carinthia such as Bad Bleiberg , Lower Austria , Styria and Tyrol .
The only known site in Switzerland so far is on the southeast flank of the Hinterer Zinggenstock near the Oberaarsee in the canton of Bern .
Tsumeb and Berg Aukas in Namibia, where crystals up to 3 cm in size were discovered, also became known due to the extraordinary discoveries of descloits .
Other locations include Algeria , Australia , Brazil , Chile , China , France . Greece , Iran , Italy , Japan , Yemen , Kyrgyzstan , the Democratic Republic of the Congo , Morocco , Mexico , Peru , Poland , Portugal , Russia , Zambia , Zimbabwe , Slovenia , Spain , South Africa , the Czech Republic , Tunisia , Turkey , Uzbekistan , the United Kingdom (Great Britain), the United States of America (USA).
use
Despite its relatively high vanadium content of up to 12.59%, Descloizit and its relative Mottramit are of little importance as ore for the extraction of vanadium.
Occasionally, descloic samples are offered in polished form for collectors .
See also
literature
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 632 (first edition: 1891).
Web links
- Mineral Atlas: Descloizit (Wiki)
- RRUFF Database-of-Raman-spectroscopy - Descloizite (English)
- American-Mineralogist-Crystal-Structure-Database - Descloizite (English)
Individual evidence
- ↑ a b c IMA / CNMNC List of Mineral Names - Mottramite (PDF 1.3 MB; February 2013)
- ↑ a b c d e 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. 459 .
- ↑ a b Descloizite . 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; 65 kB ; accessed on November 9, 2017]).
- ^ A b Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York (et al.) 1997, ISBN 0-471-19310-0 , pp. 829-830 .
- ↑ a b c d e f MinDat - Descloizite (English)
- ↑ J. Ladurner, F. Purtscheller: The great mineral book . 2nd Edition. Pinguin Verlag, Innsbruck / Tirol 1970, p. 108 .
- ^ AA Damour: Notice sur la descloizite, nouvelle espèce minérale . In: Annales de Chimie et de Physique . tape 41 , 1854, pp. 72–78 ( rruff.info [PDF; 309 kB ; accessed on November 9, 2017]).
- ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
- ↑ a b List of locations for Descloizit in the Mineralienatlas and Mindat
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia (= Dörfler Natur ). Nebel Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 166 .
- ↑ Webmineral - Descloizite (English)
- ^ Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 622-623 .
- ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 228 .