Legrandite
| Legrandite | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Zn 2 [OH | AsO 4 ] • H 2 O |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.DC.10 ( 8th edition : VII / D.02) 06.22.04.01 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | P 2 1 / c (No. 14) |
| Lattice parameters |
a = 12.80 Å ; b = 7.93 Å; c = 10.21 Å β = 104.4 ° |
| Formula units | Z = 8 |
| Frequent crystal faces | {110} |
| Physical Properties | |
| Mohs hardness | 4.5 to 5 |
| Density (g / cm 3 ) | measured: 3.98 to 4.01; calculated: 4.015 |
| Cleavage | indistinct to good after {100} |
| Break ; Tenacity | uneven; brittle |
| colour | colorless, wax yellow, orange-yellow |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.675 to 1.702 n β = 1.690 to 1.709 n γ = 1.735 to 1.740 |
| Birefringence | δ = 0.060 |
| Optical character | biaxial positive |
| Axis angle | 2V = 50 ° (measured); 52 to 62 ° (calculated) |
Legrandit is a rarely occurring minerals from the mineral class of "phosphates, arsenates, and vanadates" with the chemical composition of Zn 2 [OH | AsO 4 ] · H 2 O and chemical point of a hydrous zinc - arsenate with additional hydroxide .
Legrandite crystallizes in the monoclinic crystal system and develops prismatic crystals of up to 28 centimeters in length, which are often connected to radial or sheaf-like mineral aggregates . In its pure form it is colorless and transparent with a glass-like sheen on the surfaces. However, due to multiple refraction due to lattice construction defects or polycrystalline training, it can also be translucent white and can take on a wax-yellow to orange-yellow color due to foreign admixtures.
Etymology and history
Legrandite was first discovered in mineral samples from the “Flor de Peña” mine near Lampazos de Naranjo in the Mexican state of Nuevo León . Julien Drugman, who described the new mineral together with Max H. Hey in 1932, had received a large number of mineral samples from the widow of the Belgian engineer and mine manager Louis CA Legrand (1861–1920), including a light yellow and previously unknown substance.
Drugman and Hey named the newly discovered mineral Legrand in honor of its discoverer.
The type material of the mineral is in the Natural History Museum in London (England) under catalog no. 1932, 131 and at Harvard University in Cambridge (Massachusetts, USA) under catalog no. 92567 and in the National Museum of Natural History in Washington, DC (USA) under catalog no. 114810 kept.
classification
Already in the now outdated 8th edition of the mineral classification according to Strunz , the legrandite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "hydrous phosphates, arsenates and vanadates with foreign anions ", where together with euchroit , nissonite , Spencerite , Strashimirit and Tagilit (discredited 2006) formed the unnamed group VII / D.02 .
In the last revised and updated Lapis mineral directory by Stefan Weiß in 2018 , which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. VII / D.07-50 . In the "Lapis Classification" this also corresponds to the "phosphates, arsenates and vanadates" class, where the department "water containing phosphates, with foreign anions" where Legrandit with Cloncurryit , Domerockit , Euchroit, Nevadait , Nissonit, Ianbruceit , Kovdorskit , Lapeyreit , Spencerit, Strashimirit and Whitecapsit forms an independent but unnamed group.
The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, also assigns the legrandite to the department of “phosphates, etc. with additional anions; with H 2 O “. However, this is further subdivided according to the relative 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 can be classified in the sub-section “With only medium-sized cations; (OH etc.): RO 4 = 1: 1 and <2: 1 “can be found where it is the only member of the unnamed group 8.DC.10 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns legrandite to the class of "phosphates, arsenates and vanadates" and there to the category of "water-containing phosphates, etc., with hydroxyl or halogen". Here it can be found together with spencerite in the unnamed group 42.06.04 within the subdivision of " Water-containing phosphates etc., with hydroxyl or halogen with (AB) 2 (XO 4 ) Z q × x (H 2 O) ".
Crystal structure
Legrandite crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a = 12.80 Å ; b = 7.93 Å; c = 10.21 Å and β = 104.4 ° and 8 formula units per unit cell .
The crystal structure of Legrandit consists of edge-sharing, 6-fold coordinated Zn [6] - octahedra , the chains form parallel to a-axis [100]. These chains are eckverknüpfte AsO 4 - tetrahedra and trigonal Zn dipyramids interconnected.
Education and Locations
Legrandite is a secondary mineral that forms in the oxidation zone of zinc and arsenic deposits . It is also rarely found in granitic pegmatites . Adamin , Köttigit , Leiteit , Paradamin , pharmacosiderite , renierite , scorodite and smithsonite appear as accompanying minerals .
As a rare mineral formation, Legrandite could only be detected at a few sites, with around 20 sites (as of 2019) being known. In addition to its type locality , the “Flor de Peña” mine, the mineral also appeared in Mexico in the “El Potosí” mine near Francisco Portillo ( Chihuahua ) and in the “Ojuela” mine (Palomas Oriente) near Mapimí (Durango). The latter is also known for its exceptionally good crystal finds up to 25 centimeters in length.
In Germany, Legrandit was found in the “Silbereckle” mine near Reichenbach ( Lahr / Black Forest ) in Baden-Württemberg, on the slag heaps of the Silberhütte near Lautenthal in Lower Saxony and in the Marie mine near Wilnsdorf in North Rhine-Westphalia.
In addition, the mineral could still be found at Broken Hill in Australia, in the “Boa Vista” pegmatite near Conselheiro Pena ( Minas Gerais ) in Brazil, on several old slag heaps in the Greek community of Lavrio , in the pits “Ohgibira” near Niimi on Honshū and “ Toroku ”on Takachiho ( Kirishima volcanic area ) on Kyūshū in Japan, near Tsumeb in Namibia, on Sanyati near Kadoma in Zimbabwe and on Sterling Hill near Ogdensburg (Sussex County, New Jersey ).
See also
literature
- Julien Drugman, Max H. Hey ( crystal structure analysis by FA Bannister): Legrandite, a new zinc arsenate . In: Mineralogical Magazine . tape 23 , 1932, p. 175–178 (English, [1] [PDF; 179 kB ; accessed on May 25, 2019]).
Web links
- Mineral Atlas: Legrandite (Wiki)
- Legrandite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed on May 25, 2019 .
- American-Mineralogist-Crystal-Structure-Database - Legrandite. In: rruff.geo.arizona.edu. Retrieved May 25, 2019 .
Individual evidence
- ↑ 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. 498 .
- ^ David Barthelmy: Legrandite Mineral Data. In: webmineral.com. Retrieved May 25, 2019 .
- ↑ a b c d e f Legrandite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF]).
- ↑ a b c d Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
- ↑ a b c d e f g Legrandite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 25, 2019 .
- ^ Catalog of Type Mineral Specimens - Legrandite. (PDF 69 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed May 26, 2019 .
- ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed April 25, 2019 .
- ^ Legrandite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 25, 2019 .
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia (= Dörfler Natur ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 179 .