Pharmacosiderite

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Pharmacosiderite
Pharmacosiderite-170215.jpg
Yellowish pharmacosiderite from the Alto das Quelhas do Gestoso Mines, Gestoso, Portugal (image width: 2 mm)
General and classification
other names
  • Arsenic acid iron
  • Arsenic acid iron oxide hydrate
  • Hexahedral Lirokon Malachite
  • Cube ore
chemical formula
  • KFe 3+ 4 (AsO 4 ) 3 (OH) 4 · 6-7H 2 O
  • KFe 3+ 4 [(OH) 4 | (AsO 4 ) 3 ] • 6-7H 2 O
  • KFe 3+ 4 [(OH) 4 | (AsO 4 ) 3 ] · ≈6H 2 O
Mineral class
(and possibly department) 		Phosphates and arsenates
System no. to Strunz
and to Dana 		8.DK.10 ( 8th edition : VII / D.47)
08.22.01.01
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic-hexakistrahedral; 4  3  m
Space group P 4 3 m (No. 215)Template: room group / 215
Lattice parameters a  = 7.98  Å
Formula units Z  = 1
Frequent crystal faces {100}, {111}, { 1 11}, {110}, {011}, {122}
Twinning lamellar
Physical Properties
Mohs hardness 2.5
Density (g / cm 3 ) measured: 2.797; calculated: 2.90
Cleavage imperfect after (001)
Break ; Tenacity shell-like
colour olive green, grass green, emerald green, honey yellow to yellowish brown, dark brown
Line color greenish white
transparency transparent to translucent
shine strong glass to diamond luster, greasy luster on broken surfaces
Crystal optics
Refractive indices n α  = 1.660 to 1.697
n β  = 1.661 to 1.700
n γ  = 1.663 to 1.704
Refractive index n  = 1.687 to 1.704
Birefringence δ = 0.005
Optical character abnormal biaxial positive or negative
Axis angle 2V = 80 ° to 90 °
Other properties
Special features weakly piezoelectric and pyroelectric

Pharmacosiderite , also known as cube ore , is a generally rarely occurring mineral from the mineral class of "phosphates, arsenates and vanadates" with the chemical composition KFe 3+ 4 [(OH) 4 | (AsO 4 ) 3 ] · 6–76H 2 O and thus, from a chemical point of view, a water-containing potassium - iron - arsenate with additional hydroxide ions .

Pharmacosiderite crystallizes in the cubic crystal system and typically develops idiomorphic , cubic crystals with often diagonally striped surfaces. It can also be found in the form of granular to massive mineral aggregates . The transparent to translucent crystals are green, honey-yellow, yellowish-brown or dark-brown , depending on the amount of foreign matter, and have a glass-like to diamond-like sheen on the surface . Pharmacosiderite leaves a greenish-white line on the marking board .

Etymology and history

The mineral was first mentioned in 1786 by Martin Heinrich Klaproth in his publication Mineralogical-chemical contribution to the natural history of Cornwall minerals . In his description, however, there are two previously unknown minerals:

“The granite mountains at Carrarach, which are so rich in all types of copper [...], also provide the following two crystallizations that have not yet been determined. [...]
The first of these [...] form delicate, olive-green skewers, long towards two or three lines, sometimes single, sometimes tufted and radiant. [...]
The other crystallization, on my specimen, consists of very small, dark green cubes heaped together, with smooth and shiny surfaces [...]. You could easily think of them as small cubes of fluorspar; [...] "

Klaproth subjected both minerals to the solder tube test and correctly identified the first as "arsenic acid copper", which Robert Jameson made known from 1820 under the name oliveite . The place Carrarach given as type locality is identical to the now known place Carharrack and the tin and copper mine of the same name near St Day in the Gwennap district belonging to the English county of Cornwall .

For the second mineral, Klaproth initially also specifies copper and arsenic acid ( arsenic acid for short ) as components , although he believes the slightly different reaction before the soldering tube (less arsenic vapor development, initial expansion on carbon) and the slow melting process leading to a gray metal grain stood out. When rolled out, there were also some steel-colored areas, which is why Klaproth suspected that the compound also contained iron. Through further experiments, however, he recognized that the copper came as a foreign admixture from the copper luster , which was intimately fused with the "cube ore". Samples that have been mechanically freed from the copper luster no longer show any copper. According to analysis by Vauquelin , the composition consisted of 48% iron, 18% arsenic acid and 32% water of crystallization as well as additions of 2 to 3% carbonate of lime.

The potassium also contained , however, escapes Vauquelin just like Klaproth before him. Even Friedrich Hausmann , who in 1813 to currently applicable to name Pharmakosiderit coined, is in his description of any recent analyzes, even though the item was discovered in the meantime (1807). The name chosen by Hausmann is derived from the Greek φάρμăκου ( Farmakon ) for poison, which alludes to the content of arsenic and σίδηρος (Sideros) for iron . The Tincroft and Carharrack mines in Gwennap , Cornwall , England are considered type localities .

EGJ Hartley was able to prove for the first time in 1899 after intensive analyzes that potassium is also a component of pharmacosiderite. However, he assumes that potassium can only be integrated into the formula if some of the hydrogen in the hydroxide groups has been replaced by potassium and gives the formula as 2FeAsO 4 · Fe [O (H, K)] 3 · 5H 2 O .

The final definition of the structure and composition was not made until 1967 by MJ Buerger, WA Dollase and I. Garaycochea-Wittke on the basis of the preliminary investigation by Josef Zemann in 1948.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the pharmacosiderite belonged to the class of "phosphates, arsenates and vanadates" and there to the department of "water-containing phosphates with foreign anions ", where it was named after the "pharmacosiderite" Group "with the system no. VII / D.47 and the other members alumopharmakosiderite , bariopharmakosiderite and natropharmakosiderite .

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 pharmacosiderite to the category 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 (OH etc.) 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  > 1: 1 and <2: 1 ”can be found, where the“ pharmacosiderite group ”with the system no. 8.DK.10 and the other members Bariopharmakosiderit, Hydroniumpharmakoalumit ( IMA 2012-050 ), Hydroniumpharmakosiderit ( IMA 2010-014 ), Natropharmakoalumit ( IMA 2010-009 ), and Natropharmakosiderit Pharmakoalumit (formerly Alumopharmakosiderit ) forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the pharmacosiderite 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 in the unnamed group 42.08.01 within the subdivision “ Water-containing phosphates etc., with hydroxyl or halogen with (AB) 7 (XO 4 ) 4 Z q × x (H 2 O) ”.

Crystal structure

Pharmacosiderite crystallizes in the cubic crystal system in the space group P 4 3 m (space group no. 215) with the lattice parameter a = 7.98  Å and one formula unit per unit cell . Template: room group / 215

The crystal structure is composed of four edge-sharing (Fe, Al) [6] - octahedra (6-fold coordination ), and six AsO 4 - tetrahedra , leading to a zeolite- connected frame with large cavities. Part of the crystal water and the large cations are stored in these cavities .

properties

Pharmacosiderite is weakly piezoelectric and pyroelectric . The mineral is insoluble in water, but soluble in hydrochloric acid. If a green crystal is immersed in ammonia water (NH 4 OH), it turns red when ammonium (NH 4 ) is absorbed . The green color can be restored by immersion in dilute hydrochloric acid in a ratio of 1: 1.

When heated in front of the soldering tube , arsenic vapors develop. Pharmacosiderite initially puffs up on charcoal and the melting process that takes place until a gray metal grain is formed is slower than with the often associated oliveite. The zeolite-like bound water (up to 5 molecules of H 2 O) also escapes continuously when heated.

Education and Locations

Bluish pharmacosiderite from the Alto das Quelhas do Gestoso Mines, Gestoso, Portugal (image width: 2.5 mm)
Greenish pharmacosiderite from Wheal Gorland, St Day, Cornwall (field of view 4.3 mm × 5.9 mm)

Pharmacosiderite forms secondarily in the oxidation zone of ore deposits , but can also be caused by hydrothermal processes (epithermal) from arsenic-containing sulfides such as arsenopyrite ( arsenic gravel ) and lollingite . In addition to the olivite already mentioned, accompanying minerals include arseniosiderite , beudantite , chalcosine ( copper luster ), chalcopyrite ( copper pebbles ), jarosite , carminite , scorodite and symplesite as well as the iron oxide mixture limonite ( brown iron stone ).

As a rather rare mineral formation, pharmacosiderite can sometimes be abundant at various sites, but overall it is not very common. So far, around 450 locations for pharmacosiderite have been documented, more than half of them in Europe (as of 2018). In addition to its type locality, the Carharrack Mine at Carharrack (formerly Carrarach ) near St Day / Gwennap and the co-type locality Tincroft Mine near Illogan / Pool , the mineral could be found at many other forts in Cornwall , England , including Penlee Beach near Newlyn , in the Pednandrea Mine (Pedn-an-Drea Mine) near Redruth , the Wheal Ellen or Old Basset Mine near St Agnes , the Valley Mine, Phoenix United Mine and Craddock Moor Mine in the Liskeard administrative region of the Croft Gothal and Penberthy Croft Mine at St Hilary as well as Wheal Owles , the Botallack Mine and the Levant Mine in the St Just mining district . In addition, pharmacosiderite occurred occasionally in the English counties of Cheshire and Devon as well as in several places in the English county of Cumbria . The only other known location in the United Kingdom is the Gwaith Yr Afon mine at Goginan in the municipality of Ceredigion in Wales .

Due to extraordinary pharmacosiderite finds, the discovery areas of St Day, Liskeard and Redruth are also where cubic crystals with a diameter of up to one centimeter appeared. However, crystal sizes of up to two centimeters were also known.

Golden orange-colored pharmacosiderite cubes from the Graul mining area in the Saxon Ore Mountains ( overall size  4.1 cm × 3.3 cm × 2 cm)

In Germany Pharmakosiderit found so far in Baden-Wuerttemberg in various places in the Black Forest as, among others, on Hornbühl in Waldkirch , mine Johannis blessing at Buhler stone in the village Gutach and a granite - quarry in Menzenschwand -Vorderdorf and in the Clara mine in Oberwolfach in the Ortenau district . In Bavaria, the mineral appeared in some places in Lower and Upper Franconia and Upper Palatinate, including the iron mines near Arzberg , in the cobalt ore leading barite tunnels of the Segen Gottes mine near Huckelheim , the former Wilhelmine copper mine near Sommerkahl and on Kreuzberg at Pleystein. In Hesse, pharmacosiderite has so far only been found in a few places in the Odenwald, such as on the heaps of the copper mine at Lochborn near Bieber and in the aorite quarry (diorite migmatite) near Erlenbach . In Hesse it was found in a gabbro quarry in the Radautal near Bad Harzburg and in the Sankt Andreasberg mining area .
Well-known sites in North Rhine-Westphalia include the Leibnitz-Dante mine in the Bensberg ore district as well as the Wilder Mann , Eisenzecher Zug and the Sophie mine belonging to Storch & Schöneberg in the Siegen-Wittgenstein district. In Rhineland-Palatinate, finds from the pits Wolf near Herdorf, Käusersteimel near Kausen and Louise near Niedersteinebach in the Altenkirchen district as well as Clemenslust near Kasbach-Ohlenberg , Reichensteinerberg near Reichenstein and Virneberg near Rheinbreitbach in the Neuwied district are known. In the Harz district in Saxony-Anhalt, the mineral emerged in several pits in the Harzgerode mining district as well as in the former Enlightened Luck mine and the Louise Charlotte mine near Wernigerode . In Saxony it was mainly found in the Erzgebirge at the Greifensteinen and the Sauberg mine near Ehrenfriedersdorf, in the St. Georg, Daniel, Güldener Falk and Rappold mines in the Schneeberg mining district, and in the Gottes Geschick, St. Katharina and Stamm Asser mines in the mining area Gray . In the Saxon Vogtland, among other things, the tin mine Grube Tannenberg and in Thuringia the quartz porphyry quarry on Kuhberg in the municipality of Neumühle / Elster and a copper mine on Bergmannskopf near Gräfenroda are known as locations for pharmacosiderite.

In Austria, pharmacosiderite has so far been found mainly in Carinthia (Knichtelager, Althaus pit), Salzburg (Anna, Daniel and Barbarastollen) and Styria ( Straßegg , Wildfrauengrotte, Zinkwand ). The mineral also appeared in an antimony mine near Stadtschlaining in Burgenland, on Knappenberg near Hirschwang on the Rax in Lower Austria, on Silberberg in the Brixlegg - Rattenberg area and in the Großstroheim quarry near Eferding in Upper Austria.

In Switzerland, pharmacosiderite is so far only known from the Hochmättli in the canton of Glarus and from the Binntal (Chummibort glacier, Hillehorn, Wannigletscher), the Turtmann valley (Pipjitälli) and the Val d'Anniviers (mine des Bourrimonts near Ayer and mine de Collioux inférieur near Saint-Luc VS ).

Other locations are in Australia, Brazil, Chile, France, Greece, Italy, Japan, Canada, Morocco, Mexico, New Zealand, Norway, Poland, Portugal, Spain, Slovakia, South Africa, the Czech Republic and the United States of America.

See also

literature

Web links

Commons : Pharmacosiderite  - collection of images, videos and audio files

Individual evidence

  1. ^ A b Karl Caesar von Leonhard: Handbuch der Oryktognosie: for academic lectures and for self-study . Mohr and Winter, Heidelberg 1821, p. 363 ( limited preview in Google Book search).
  2. ↑ a b c d Joh. Friedr. Ludw. Hausmann: Handbook of Mineralogy . tape 1-3 . Vandenhoeck & Ruprecht , Göttingen 1813, p. 1065-1067 ( limited preview in Google Book Search).
  3. ↑ a b c d e Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp.  652 (first edition: 1891).
  4. ^ IMA / CNMNC List of Mineral Names; September 2018 (English, PDF 1.7 MB)
  5. ↑ a b c 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 .
  6. ^ A b 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.  514 .
  7. ↑ a b c d M. J. Buerger , WA Dollase, I. Garaycochea-Wittke: The structure and composition of the mineral pharmacosiderite . In: Journal of Crystallography . tape  125 , 1967, pp. 92-108 ( rruff.info [PDF; 749 kB ; accessed on November 20, 2018]).
  8. ↑ a b c d e f g Pharmacosiderites . 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 November 19, 2018]).
  9. ^ A b c d e Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  641 .
  10. ↑ a b c d e f g Mindat - Pharmakosiderite (English)
  11. ^ Martin Heinrich Klaproth: Mineralogical-chemical contribution to the natural history of Cornwallic minerals . In: Writings of the Society of Friends of Natural Science in Berlin . tape 7 , no. 1 , 1786, p. 160–161 ( digitized from Harvard University ).
  12. ↑ David Aubrey-Jones: Oliveite. In: britishrocks.com. April 19, 2009. Retrieved November 20, 2018 .
  13. ↑ Mineral Atlas : Carharrack Mine
  14. ↑ Franz Ambros Reuss : Textbook of mineralogy according to the DBR Karsten mineralogical tables . 2nd part, 4th volume. Friedrich Gotthold Jacobäer, Leipzig 1803, p.  153–155 ( limited preview in Google Book search).
  15. ↑ EGJ Hartley: Communications from the Oxford Mineralogical Laboratory. On the Constitution of the Natural Arsenates and Phosphates . In: Mineralogical Magazine . tape 12 , 1899, pp. 152–158 (English, minersoc.org [PDF; 278 kB ; accessed on November 20, 2018]).
  16. ↑ J. Zemann: Formula and structure type of the pharmacosiderite . In: Tschermaks Mineralogische und Petrographische Mitteilungen . tape 1 , 1948, p. 1-13 , doi : 10.1007 / BF01130556 .
  17. ↑ 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. 908-909 .
  18. ↑ a b Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Dörfler Natur ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 188 .
  19. ↑ Mindat - Number of localities for pharmacosiderites (English)
  20. ↑ a b List of locations for pharmacosiderite in the Mineralienatlas and Mindat