Kingstonite

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Kingstonite
General and classification
other names

IMA 1993-046

chemical formula Rh 3 S 4
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.DA.25 ( 8th edition : II / D.02)
02.10.02.04
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 10.4616 (5)  Å ; b  = 10.7527 (5) Å; c  = 6.2648 (3) Å
β  = 109.000 (5) °
Formula units Z  = 6
Physical Properties
Mohs hardness 6th
Density (g / cm 3 ) calculated: 7.52
Cleavage good after [001]
Break ; Tenacity slightly mussel-like; brittle
colour brownish gray
Line color black
transparency opaque
shine Metallic luster

Kingstonite is a very rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the monoclinic crystal system with the idealized chemical composition Rh 3 S 4 , so it is chemically a rhodium sulfide . Since kingstonite in nature always contains small amounts of iridium and / or platinum in addition to rhodium , the formula is usually given as (Rh, Ir, Pt) 3 S 4 . The elements indicated in the round brackets can represent each other in the formula ( substitution , diadochie), but are always in the same proportion to the other components of the mineral.

So far, kingstonite could only be found in the form of hypidiomorphic to xenomorphic inclusions of about 15 to 40 µm in size in a platinum-iron nugget . The mineral is opaque, brownish-gray in color with black streak color and has a metallic sheen .

Etymology and history

Kingstonite was first discovered in 1993 on the Bir Bir River near Yubdo (Joubdo; Youbdo; Joubda) near Gimbi in the Ethiopian region of Oromia and described by CJ Stanley, AJ Criddle, J. Spratt, AC Roberts, JT Szymański and MD Welch, who made the mineral named after Gordon Kingston (formerly of Cardiff University) to recognize his contributions to the mineralogy of the platinum group elements and the geology of the ore deposits.

classification

Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the kingstonite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfides with the molar ratio of metal: sulfur, selenium, tellurium <1: 1", where together with cuproiridsite , cuprorhodsite , ferrorhodsite , malanite and xingzhongite it formed the independent group II / D.02 .

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 kingstonite to the class of “sulfides and sulfosalts”, but in the newly defined section of “metal sulfides with the substance ratio M : S = 3: 4 and 2: 3 “. This section is further subdivided according to the exact substance quantity ratio, so that the mineral can be found according to its composition in the sub-section "M: S = 3: 4", where it is the only member of the unnamed group 2.DA.25 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns kingstonite to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here he is together with Wilkmanit , Brezinait and Heideit in the "Wilkmanit group" with the system no. 02.10.02 within the subsection of " Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 3: 4 ".

Crystal structure

Kingstonite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 10.4616 (5)  Å ; b  = 10.7527 (5) Å; c  = 6.2648 (3) Å and β = 109.000 (5) ° and 6 formula units per unit cell . Template: room group / 12

Education and Locations

Nothing is known about the exact formation conditions so far, as Kingstonite has only been found in one sample, a 1.5 cm nugget and type material of the mineral prassoite . The deposit from which the sample originates consists of the rocks dunite and pyroxenite . Bowieite , cuprorhodsite , ferrorhodsite , isoferroplatinum , laurite , osmium and tetraferroplatinum could be detected in other mineral associations .

Apart from its type locality Bir Bir River in Ethiopia, the mineral could not be detected at any other place so far (status: 2011).

See also

literature

  • Kingstonite . 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; 318 kB ; accessed on June 20, 2019]).

Web links

Individual evidence

  1. ↑ a b Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: March 2019. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, March 2019, accessed May 20, 2019 .
  2. ↑ a b c d e f g h CJ Stanley, AJ Criddle, J. Spratt, AC Roberts, JT Szymański, MD Welch: Kingstonite, (Rh, Ir, Pt) 3 S 4 , a new mineral species from Yubdo, Ethiopia . In: Mineralogical Magazine . tape 69 , August 2005, p. 447–453 (English, rruff.info [PDF]).
  3. ^ A b c Andrew J. Locock, Paula C. Piilonen, T. Scott Ercit, Ralph Rowe, Uwe Kolitsch: New Mineral Names . In: American Mineralogist . tape 91 , 2006, p. 710–715 (English, minsocam.org [PDF; 157 kB ; accessed on June 20, 2019]).
  4. ↑ Kingstonite. In: mindat.org. Hudson Institute of Mineralogy, accessed June 20, 2019 .