Kalungaite

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Kalungaite
General and classification
other names

IMA 2004-04

chemical formula PdAsSe
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.EB.25
02.12.03.16
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic-disdodecahedral; 2 / m  3
Space group Pa 3 (No. 205)Template: room group / 205
Lattice parameters a  = 6.089 (4)  Å
Formula units Z  = 4
Physical Properties
Mohs hardness 4 to 5 (VHN 25 = 429 to 455, average 438 kg / mm 2 )
Density (g / cm 3 ) calculated: 7.59
Cleavage is missing
Break ; Tenacity uneven; brittle
colour lead gray
Line color black
transparency opaque (opaque)
shine Metallic luster

Kalungaite is a very seldom occurring mineral from the mineral class of " sulfides and sulfosalts " with the chemical composition PdAsSe and thus, chemically speaking, a palladium - arsenic - selenide . As close relatives of the sulfides, the selenides are placed in the same class.

Kalungaite crystallizes in the cubic crystal system , but has so far only been found in the form of platy, irregular mineral aggregates up to about 0.3 mm in size. The mineral is in any form opaque ( opaque ) and displays on the surfaces of lead-gray in reflected light and gray cream to cream-colored, aggregates have a metallic luster . His line color , on the other hand, is black.

Etymology and history

The compound PdAsSe could already be synthesized in 2001 by Aloys J. Foecker and Wolfgang Jeitschko. The crystal structure could also be determined from the synthesis .

Kalungaite was first discovered as a natural mineral formation in the Buraco do Ouro gold mine ( 13 ° 47 ′ 45 ″  S , 47 ° 27 ′ 35 ″  W ) near Cavalcante in the Brazilian state of Goiás . The mineral was analyzed and described by NF Botelho, MA Moutra, RC Peterson, CJ Stanley, and DVG Silva, who named it after the Kalunga community who lived as descendants of African slaves outside of Cavalcante and other nearby towns.

The test results and the chosen name for the newly discovered mineral were submitted to the International Mineralogical Association for examination in 2003 (internal submission number of the IMA: 2004-04), which recognized the Kalungaite as an independent mineral type. The publication of the first description followed three years later in Mineralogical Magazine .

The type material of the mineral in the form of a polished thin section was according to the first description in the Natural History Museum in London , England under the catalog no. BM2004,35 kept. However, this information is not confirmed in the IMA type mineral catalog.

classification

Since the Kalungaite was only recognized as an independent mineral in 2003 and this was only published in 2006, it is not yet listed in the outdated 8th edition of the mineral classification according to Strunz . Only in the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , was the mineral given the system and mineral number. II / D.18-43 . In the “Lapis system” this corresponds to the class of “sulfides and sulfosalts” and there the section “sulfides with [the molar ratio] metal: S, Se, Te <1: 1”, where kalungaite together with cobaltite , gersdorffite , hollingworthite , Irarsit , Jolliffeit , Milotait , Platarsit , Tolovkit , Ullmannit and Willyamit form the "cobaltite group" (status 2018).

The 9th edition of Strunz's mineral systematics, which has been valid since 2001 and was updated by the IMA until 2009, classifies the Kalungaite in the category of “Metal sulfides with M: S ≤ 1: 2”. This is further subdivided according to the exact molar ratio and the predominant metals in the compound, so that the mineral can be found in the sub-section "M: S = 1: 2, with Fe, Co, Ni, PGE etc." according to its composition where it together with Changchengit , cobaltite, Gersdorffit-P2 1 3 , Gersdorffit-Pa 3 , Gersdorffit-Pca2 1 , Hollingworthit, Irarsit, Jolliffeit, Krutovit , Maslovit , Mayingit , Michenerit , Milotait, Padmait , Platarsit, Testibiopalladit , Tolovkit, Ullmannit and Willyamit the "Gersdorffitgruppe" with the system no. 2.EB.25 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Kalungaite to the class of “sulfides and sulfosalts” and there to the “sulfide minerals” category. Here it is in the " cobaltite group (cubic or pseudocubic crystals) " with the system no. 02.12.03 within the subsection "Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 1: 2".

Chemism

The idealized (theoretical) composition of Kalungaite (PdAsSe) consists of palladium (Pd), arsenic (As) and selenium (Se) in a molar ratio of 1: 1: 1. This corresponds to a mass fraction calculated from the atomic weight of the elements (% by weight ) of 40.88% Pd, 28.78% As and 30.33% Se. Since arsenic and selenium behave like sulfur- like non - metals in the compound , they are added together and the molar ratio is given as metal: sulfur (selenium, tellurium) = 1: 2.

Eight measurements with a Cameca -SX50 microprobe at the edge and in the core of the type material resulted in an average of slightly different compositions of 41.32% by weight Pd, 27.49% by weight As and 27.67% by weight Se and additionally low contents of 1.59% by weight of antimony (Sb), 1.22% by weight of sulfur (S) and 0.35% by weight of bismuth (Bi), which replace some of the arsenic and selenium .

Crystal structure

Kalungaite crystallizes cubically in the space group Pa 3 (space group no. 205) with the lattice parameter a  = 6.089 (4)  Å and four formula units per unit cell . Template: room group / 205

Education and Locations

Kalungait formed in a hydrothermal Gold - deposit in the quartz - and muskovitreichen zones of a Mylonitgesteins that in peraluminosen (aluminum supersaturated) granite penetrated. In addition to gold, bohdanowiczite , chalcopyrite , clausthalite , guanajuatite , padmaite , sperrylite and stibiopalladinite as well as an unnamed Pb-Bi-Se-S mineral were found as accompanying minerals . In addition to muscovite and quartz, magnetite and tourmaline were added as gang minerals .

So far, Kalungaite could only be found at its type locality , the Buraco do Ouro gold mine near Cavalcante in Brazil.

See also

literature

  • Aloys J. Foecker, Wolfgang Jeitschko: The atomic order of the pnictogen and chalcogen atoms in equiatomic ternary compounds TPnCh (T = Ni, Pd; Pn = P, As, Sb; Ch = S, Se, Te) . In: Journal of Solid State Chemistry . tape 162 , 2001, p. 69-78 , doi : 10.1006 / jssc.2001.9342 (English).
  • NF Botelho, MA Moutra, RC Peterson, CJ Stanley, DVG Silva: Kalungaite, PdAsSe, a new platinum-group mineral from the Buraco do Ouro gold mine, Cavalcante, Goiás State, Brazil . In: Mineralogical Magazine . tape 70 , no. 1 , 2006, p. 123–130 , doi : 10.1180 / 0026461067010318 (English, rruff.info [PDF; 1.1 MB ; accessed on July 6, 2020]).
  • Paula C. Piilonen, Ralph Rowe, T. Scott Ercit, Andrew J. Locock: New mineral names . In: American Mineralogist . tape 91 , 2006, p. 1452–1457 , doi : 10.2138 / am.2006.470 (English, rruff.info [PDF; 141 kB ; accessed on July 6, 2020]).

Web links

Individual evidence

  1. ↑ a b c Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: July 2020. (PDF; 2.44 MB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, July 2020, accessed July 6, 2020 .
  2. ↑ a b c d e f g h i j k l m n o p NF Botelho, MA Moutra, RC Peterson, CJ Stanley, DVG Silva: Kalungaite, PdAsSe, a new platinum-group mineral from the Buraco do Ouro gold mine, Cavalcante, Goiás State, Brazil . In: Mineralogical Magazine . tape 70 , no. 1 , 2006, p. 123–130 , doi : 10.1180 / 0026461067010318 (English, rruff.info [PDF; 1.1 MB ; accessed on July 6, 2020]).
  3. ↑ a b Kalungaite . 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; 117  kB ; accessed on July 6, 2020]).
  4. ↑ Aloys J. Föcker, Wolfgang Jeitschko: The atomic order of the pnictogen and chalcogen atom in equiatomic ternary compounds TPnCh (T = Ni, Pd; Pn = P, As, Sb, Ch = S, Se, Te) . In: Journal of Solid State Chemistry . tape 162 , 2001, p. 69-78 , doi : 10.1006 / jssc.2001.9342 (English).
  5. ↑ Catalog of Type Mineral Specimens - K. (PDF 96 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed July 6, 2020 .
  6. ↑ 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 .
  7. ↑ Ernest H. Nickel , Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1.82 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed July 6, 2020 .
  8. ↑ Kalungaite. In: Mineralienatlas Lexikon. Stefan Schorn u. a., accessed on July 6, 2020 .
  9. ↑ Find location list for Kalungaite in the Mineralienatlas and Mindat , accessed on July 6, 2020.