Maldonite

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Maldonite
Maldonite (bismuth gold) - Mineralogisches Museum Bonn2.jpg
Maldonite from the Eagle Hawk Union Mine, Maldon, Victoria (Australia)
General and classification
other names

Bismuth gold

chemical formula Au 2 bi
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.AA.40 ( 8th edition : II / A.03)
01.01.03.01
Crystallographic Data
Crystal system cubic
Crystal class ; symbol cubic hexakisoctahedral; 4 / m  3  2 / m
Space group Fd 3 m (No. 227)Template: room group / 227
Lattice parameters a  = 7.98  Å
Formula units Z  = 8
Physical Properties
Mohs hardness 1.5 to 2
Density (g / cm 3 ) measured: 15.46; calculated: 15.70
Cleavage clearly after {001} and {110}
Break ; Tenacity shell-like
colour silver-gray, tarnished copper-red to black
Line color Please complete!
transparency opaque
shine Metallic luster

Maldonite , also known as bismuth gold out of date , is a rarely occurring mineral from the mineral class of “ sulfides and sulfosalts ” with the chemical composition Au 2 Bi and thus consists of gold and bismuth in a molar ratio of 2: 1.

Maldonite crystallizes in the cubic crystal system and develops massive grains or thin coatings, often in adhesions of gold and bismuth of a silver-gray color with a pinkish tinge on fresh surfaces.

Etymology and history

The mineral was first found in 1869 by Georg Heinrich Friedrich Ulrich (1830-1900) in the type locality Nuggety Reef in Maldon in the Australian state of Victoria . It is named after this too.

classification

In the Strunz system , maldonite is one of the alloys and alloy-like compounds, a subgroup of sulfides and sulfosalts. After the 8th edition, it forms a group together with Bezsmertnovit and Bilibinskit . In the 9th edition it forms a separate subgroup of the compounds of semi-metals with copper, silver and gold .

In the Dana systematics, in contrast to the Strunz systematics, it does not belong to the sulfides, but forms a separate subgroup of the metallic elements apart from the platinum metals .

Crystal structure

Maldonite crystallizes in the cubic crystal system in the space group Fd 3 m (space group no. 227) with the lattice parameter a  = 7.98  Å and eight formula units per unit cell . Template: room group / 227

Education and Locations

Maldonite forms under hydrothermal conditions in gold- quartz veins and skarns at temperatures below 373 ° C. It is associated with gold, bismuth, bismuthinite , joseit , arsenopyrite , lollingite , pyrite , pyrrhotite , chalcopyrite , cubanite , scheelite , apatite , siderite , calcite and quartz.

EMS - recording of the phases maldonite, bismuth , bismuthinite , pyrite and Au-Ag in quartz from the Ädelfors gold mine . The arrangement in so-called trails, probably former cracks, is striking.

In addition to the type locality and other finds in Australia, there are other finds from Mariana in Brazil, Hedley in Canada , Coyhaique in Chile , Tongling in China , Sušice and Humpolec in the Czech Republic , Sweden ( Ädelfors ), Finland , Bonnac and Salsigne in France , Laurion in Greece , the Ōsumi Peninsula in Japan , the High Atlas in Morocco , Karibib in Namibia , Radzimowice in Poland , Nucet in Romania , Russia, Rustenburg in South Africa, the US states Alaska , California , Idaho and North Carolina , as well as Harare and Masvingo in Zimbabwe .

See also

literature

  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 415 (first edition: 1891).
  • Maldonite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 63 kB ; accessed on September 15, 2017]).

Web links

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

Individual evidence

  1. ↑ Sample label filled in by Ulrich, who first described it himself
  2. ^ 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.  58 .
  3. ↑ a b c Maldonite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 63  kB ; accessed on September 15, 2017]).
  4. ↑ Australian Dictionary of Biography - Ulrich, Georg Heinrich Friedrich (George Henry Frederick) (1830–1900)
  5. ^ Jonas Börje Lundin: Investigation of bismuth-bound gold mineralization near Vetlanda, southern Sweden . 2015, doi : 10.13140 / RG.2.1.4330.2483 ( researchgate.net [PDF; 9.6 MB ; accessed on September 14, 2017]).
  6. ↑ Find location list for maldonite at the Mineralienatlas and at Mindat