Arsenic
| Arsenic | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1979-030 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.BH.35 ( 8th edition : VII / B.27) 41.05.01.09 |
| Similar minerals | Adamin, tsumcorite, mimetite |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-disphenoidic; 222 |
| Space group | P 2 1 2 1 2 1 (No. 19) |
| Lattice parameters | a = 7.646 Å ; b = 9.363 Å; c = 6.077 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | {001}, {011}, {101}, {111} |
| Physical Properties | |
| Mohs hardness | ≈ 4 |
| Density (g / cm 3 ) | 5.67 (measured); 6.57 (calculated) |
| Cleavage | no |
| Break ; Tenacity | not specified; not specified |
| colour | pale yellow, light orange-yellow, bright green, dark green, gray-brown |
| Line color | White |
| transparency | transparent |
| shine | Semi-diamond luster |
| Crystal optics | |
| Refractive indices |
n α = 1.990 n β = 2.030 n γ = 2.035 |
| Birefringence | δ = 0.045 |
| Optical character | biaxial negative |
| Axis angle | 2V = ≈ 30 ° (measured) |
| Pleochroism | none |
| Other properties | |
| Chemical behavior | poorly soluble in hot nitric acid |
Arsenic is a rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the orthorhombic crystal system with the chemical composition PbZn (OH) (AsO 4 ) and is thus chemically seen a lead - zinc - arsenate with additional hydroxide ions (OH - ).
Arsendescloizit develops tabular crystals up to 0.5 mm in size according to {001} , which typically come together to form rosette-shaped or warty to grape-like aggregates . The type locality of the mineral is the Tsumeb Mine, where it appeared in cavities in the tennantitic ore and was accompanied there by willemite , chalcosine , mimetite , quartz and goethite . The type stage of the arsendescloicite is also one of two stages at which the uranium mineral kasolite was discovered in Tsumeb.
Etymology and history
The discoverer of the Arsendescloizit is considered to be Wolfgang Bartelke , who noticed a pale yellow mineral resembling Adamin or Tsumcorite on a step found in the Tsumeb Mine and who made this step available to the authors of the type publication for identification. Corresponding investigations showed that the X-ray diffraction pattern of the mineral was almost identical to that of Descloizit , but that the mineral did not contain any traces of vanadium . As a result, a new mineral was present, likely Descloizit's arsenate analogue. The new mineral was recognized by the International Mineralogical Association (IMA) in 1979 and described as an arsenic in 1980 by Paul Keller from the University of Stuttgart and Pete J. Dunn from the Smithsonian Institution . The authors named the mineral because of its chemical composition and structural relationship with Descloizit.
Type material of the mineral is in the archive of the University of Stuttgart - "Mineralogical Collection Prof. Keller" (holotype, collection no. TM-79.30-B76 at location 0/824-s27 / 2) and at the National Museum of Natural History , Washington, DC , USA (Cotyp, collection no. 148303).
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the arsenic belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates with foreign anions ", where it together with Čechit , Descloizit , Mottramit and pyrobelonite 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), assigns the arsenic decoicite to the class of “phosphates, arsenates and vanadates” and there to the department of “phosphates etc. with additional anions; without H 2 O “. However, this section is further subdivided according to the size of the cations involved and their molar ratio to the phosphate, arsenate or vanadate complex RO 4 , so that the mineral is classified in the sub-section “With medium-sized and mostly large cations; (OH etc.): RO 4 = 1: 1 “is to be found, where together with Adelite , Austinite , Cobaltaustinite , Duftite , Gabrielsonite , Gottlobit , Konichalcite , Nickelaustinite and Tangeit the“ Adelite Group ”with the system no. 8.BH.35 forms.
The systematics of minerals according to Dana also assigns the arsenic decoicite to the class of "phosphates (and relatives)", but there in the department of "anhydrous phosphates etc., with hydroxyl or halogen". Here, too, it is together with Adelite, Konichalcite, Austinite, Duftit-beta , Gabrielsonite, Tangeit, Nickelaustinite, Cobaltaustinite and Gottlobit in the "Adelite group" with the system no. 41.05.01 to be found within the sub-section of " anhydrous phosphates etc., with hydroxyl or halogen and the general formula (AB) 2 (XO 4 ) Z q ".
Chemism
Arsenic desiccant has the measured composition Pb 1.06 (Zn 1.03 Fe 0.02 ) Σ = 1.05 (AsO 4 ) (OH) 1.4 , which can be written simply as PbZn (OH) (AsO 4 ) and Requires 18.99% ZnO, 52.09% PbO, 26.82% As 2 O 5, and 2.10% H 2 O.
Arsenic descloicite is the arsenate-dominant analogue of vanadate-dominated descloicite, but can also be understood as a zinc-dominant analogue of Cu 2+ -dominated fragrance or as a lead- dominant analogue of Ca-dominated austinite. The chemical analysis of the type level did not reveal any levels of vanadium, zinc or lead.
Crystal structure
Arsenic desiccate crystallizes in the orthorhombic crystal system in the space group P 2 1 2 1 2 1 (space group number 19) with the lattice parameters a = 7.646 Å ; b = 9.363 Å and c = 6.077 Å as well as four formula units per unit cell .
The crystal structure of arsenic descloicite consists of relatively regular [AsO 4 ] tetrahedra , [Zn (OH) 2 O 4 ] octahedra and [Pb (OH) O 7 ] polyhedra . The [Zn (OH) 2 O 4 ] octahedra are connected by common edges and form linear, weakly kinked chains that run parallel to the screw axis c. The chains are also linked to one another via three corner points of the [AsO 4 ] tetrahedra and in this way form an open, three-dimensional network structure. The channels contained therein parallel to the a-axis [100] contain [Pb (OH) O 7 ] polyhedra with common edges and corners, which are also connected by hydrogen bonds .
Arsendescloicite is isotypic (isostructural) to those orthorhombic minerals of the Adelite group, which crystallize in the space group P 2 1 2 1 2 1 (space group no. 19) and whose lattice parameters are in the following ranges: a = 7.39–7 , 77, b = 8.89-9.36, c = 5.83-6.08 Å, Z = 4. Your general formula is VIII M1 2+ VI M2 2+ (OH) [XO 4 ] with VIII M1 2+ = Ca and Pb, VI M2 2+ = Mg, Co, Ni, Cu and Zn, X = As 5+ .
properties
morphology
According to {001}, Arsendescloizit forms platy to tabular as well as wedge-shaped crystals up to a maximum of 1 mm in size, on which in addition to the supporting form, the basic pinacoid {001}, the prisms {011} and {101} as well as the right disphenoid {111} are identified have been. However, since in the crystal class 222 the form {111} is not a dipyramid with eight faces, but a disphenoid with only four faces, the arsenic decloicit according to the crystal drawing in the original publication must have another form, namely a left disphenoid. In the adjacent drawing, {1 1 1} was used for this. Both disphenoids together then have eight faces and thus correspond to an orthorhombic pyramid of the crystal class mmm. In the Tsumeb Mine, the crystals come together to form rosette-shaped aggregates; warty to grape-like aggregates are characteristic of the Ojuela Mine in Mexico.
physical and chemical properties
The crystals of arsendescloicite are pale yellow, light orange-yellow, bright green or dark green to gray-brown, their line color is indicated as white. The surfaces of the transparent crystals have a brilliant semi-diamond-like sheen , which is also underlined by the very high values for light refraction (n α = 1.990, n γ = 2.035).
The mineral does not have any cleavage properties , information on breakage (mineral) and tenacity are missing. With a Mohs hardness of ≈ 4, arsenic is one of the medium-hard minerals that, like the reference mineral fluorite, can be easily scratched with a pocket knife. The measured density of the mineral is 5.67 g / cm³, its calculated density is 6.57 g / cm³.
Arsenic decoicite is only sparingly soluble in hot nitric acid.
Education and Locations
Arsendescloizit is a typical secondary mineral and formed in the Tsumeb Mine in the second (lower) and third oxidation zone from lead and zinc-containing sulfides (galena, sphalerite), the arsenic originating from the decomposition of the arsenic pale ore tennantite.
Arsendescloizit was first observed in the solution cavities of a matrix of tennantite and chalcosine in the Tsumeb mine and was there from water-clear willemite crystals, idiomorphic chalcosine crystals, quartz, corroded mimetite, goethite, gray casolite and the previously unknown mineral GS 11, a colorless Ca-Pb-Zn-As mineral, accompanied. The succession observed is (from the oldest to the youngest mineral) chalcosine → quartz → mimetite → arsendescloicite → goethite → willemite. In the Mina Ojuela, white to beige-yellow mimetesite, emerald-green, spherical adamin and hydrozincite belong to the paragenesis of arsenic descloicite.
As a rare mineral formation, Arsendescloizit could so far (as of 2016) only be described from about 20 other sites in addition to its type locality . As a type locality which is considered world-famous, in dolomite stones fitting, hydrothermal , poly- Cu-Pb-Zn-Ag-Ge-Cd deposit of "Tsumeb Mine" (Tsumcorp Mine) in Tsumeb region Oshikoto , Namibia , where a precisely Fund point for the Type Level Does not exist. Further stages with arsenic desiccation come from the so-called third oxidation zone in the area of the 30th level.
The “Red Bird Mine” near Lovelock , Pershing County , Nevada , USA, has delivered the world's best arsenic loicite specimens with orange-colored crystals up to 1 mm in size accompanied by smithsonite . Other sites in the United States include the Tonopah-Belmont Mine at Belmont Mountain, Tonopah , Osborn District, Big Horn Mts, Maricopa County in Arizona , the Scratch Awl Mine, Philipsburg District, Granite County in Montana , the Silver Coin Mine "at Valmy, Iron Point District, Humboldt Co. , and the" Illinois Mine "at Marble Camp, Lodi District, Lodi Hills, Nye County , both in Nevada, as well as the" Cleveland Mine "at Adams Mountain, Deer Trail & Cedar Canyon Districts, Huckleberry Range, Stevens County , Washington .
Possibly the most beautiful specimens with dark green arsenic originate from the Lugar (mining site) "San Juditas" of the "Mina Ojuela" near Mapimí , Municipio de Mapimí , Durango , Mexico .
In Germany , Arsendescloizit is known from the “Michael” mine in the hamlet near Lahr , Black Forest , Baden-Württemberg , and from the Bad Ems district , Lahntal , Rhineland-Palatinate . Two deposits are known from Austria , the “St. Anna ”(“ Hocheck ”mine) near Annaberg , Mostviertel , Lower Austria , and the“ Fuchsloch ”near Brixlegg-Rattenberg, Schwaz - Brixlegg im Inntal district , Tyrol . In Switzerland , Arsendescloizit was found in the dolomite outcrops on the Reckibach not far from Binn in the Binntal , Canton of Valais .
In Europe, more finds were made at the “Shaft No. 132 "of the" Christiana Mine "near Agios Konstantinos (Kamariza) and in the" Plaka Mine No. 80 ”(Filoni 80) near Plaka, all in the Lavrion District, Attica region , Greece , in the“ Mina da Herdade de Vila Ruiva ”near Sobral da Adiça , Moura , Beja District , Portugal , as well as in the“ Old Sandbed Mine ” Caldbeck Fells in the English county of Cumbria in the United Kingdom .
Finally, Arsendescloizit is also from the "Beltana Mine" near Puttapa , Leigh Creek , Flinders Ranges , South Australia , Australia , the tin-polymetallic ore field of Gejiu (the world's largest tin ore field ), near the city of the same name, Honghe Autonomous District , Yunnan Province , China , and from the “Toroku Mine” near Takachiho, Miyazaki Prefecture , Kyushu Region , Japan .
use
While the Descloizit was used as vanadium ore, the arsenic descloicit is only of interest to mineral collectors due to its rarity.
See also
literature
- Arsendescloicite . 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; 64 kB ; accessed on August 15, 2018]).
- Paul Keller, Pete J. Dunn: Arsendescloizite a new mineral from Tsumeb . In: Mineralogical Record . tape 13 , no. 3 , 1982, pp. 155–157 (English, rruff.info [PDF; 1.7 MB ; accessed on August 15, 2018]).
- Paul Keller, Falk Lissner, Thomas Schleid: The crystal structure of arsendescloizite, PbZn (OH) [AsO 4 ], from Tsumeb (Namibia) . In: New Yearbook Mineralogy, monthly books . tape 2003 , no. 8 , 2003, p. 374-384 (English).
Web links
- Mineral Atlas: Arsendescloizit (Wiki)
- Mindat - Arsendescloizite (English)
- Webmineral - Arsendescloizite (English)
- RRUFF Database-of-Raman-spectroscopy - Arsendescloizite (English)
- American-Mineralogist-Crystal-Structure-Database - Arsendescloizite (English)
Individual evidence
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae Paul Keller, Pete J. Dunn: Arsendescloizite a new mineral from Tsumeb . In: Mineralogical Record . tape 13 , no. 3 , 1982, pp. 155–157 (English, rruff.info [PDF; 1.7 MB ; accessed on August 15, 2018]).
- ^ 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. 458 (English).
- ^ A b c d Paul Keller, Falk Lissner, Thomas Schleid: The crystal structure of arsendescloizite, PbZn (OH) [AsO 4 ], from Tsumeb (Namibia) . In: New Yearbook Mineralogy, monthly books . tape 2003 , no. 8 , 2003, p. 374-384 (English).
- ↑ a b c d e Arsendescloizite . 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; 64 kB ; accessed on August 15, 2018]).
- ↑ a b c Georg Gebhard: Tsumeb . 1st edition. GG Publishing, Grossenseifen 1999, p. 251 .
- ↑ a b c Tom P. Moore, Peter KM Megaw: Famous mineral localities: The Ojuela mine, Mapimi, Durango, Mexico . In: The Mineralogical Record . tape 34 , no. 5 , 2003, p. 1-91 (English).
- ↑ a b c Mindat - Arsendescloizite (English)
- ↑ a b Georg Gebhard: Tsumeb . 1st edition. Christel Gebhard-Giesen, Reichshof 1991, p. 172 .
- ↑ Type mineral catalog Germany - storage of the holotype stage Arsendescloizit
- ↑ Mindat - Number of localities for Arsendescloizit (English)
- ↑ a b List of locations for Arsendescloizit in the Mineralienatlas and Mindat