Mckinstryit

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Mckinstryit
Mckinstryite (Alice Chodura) .JPG
Mckinstryit from Silver City, New Mexico, USA
General and classification
other names

IMA 1966-012

chemical formula
  • idealized: Ag 4.92 Cu 3.08 S 4 or ~ Ag 5 Cu 3 S 4
  • generalized: Ag 5-x Cu 3 + x S 4 (x ≈ 0 to 0.28)
  • formerly: (Ag, Cu) 2 S
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.BA.25b ( 8th edition : II / B.06)
04/02/05/01
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m 2 / m 2 / m
Room group (no.) Pnma (No. 62)
Lattice parameters a  = 14.047  Å ; b  = 7.805 Å; c  = 15.691 Å
Formula units Z  = 8
Physical Properties
Mohs hardness not defined (VHN 25 = 43 to 45 kg / mm 2 )
Density (g / cm 3 ) measured: 6.61; calculated: 6.57
Cleavage indistinct
Break ; Tenacity slightly mussel-like
colour steel gray, dark gray to black
Line color dark steel gray
transparency opaque
shine Metallic luster

McKinstryite is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the orthorhombic crystal system with the idealized composition ~ Ag 5 Cu 3 S 4 . Since the content of silver and copper in the formula can vary slightly due to the structure, the generalized formula Ag 5-x Cu 3 + x S 4 is often given with x ≈ 0 to 0.28.

Mckinstryit forms granular mineral aggregates of intergrown crystals up to about three millimeters in size . It is opaque in every form and shows a steel-gray color on fresh surfaces and a light grayish-white color on polished surfaces. After a long time in the air, it turns dark gray to black.

Etymology and history

Mckinstryite was first found in the "Foster Mine" near Coleman Township in the Canadian province of Ontario and was described in 1966 by Brian J. Skinner , John Leslie Jambor and Malcolm Ross , who named the mineral after the American geology professor Hugh Exton McKinstry (1896–1961 ) named.

classification

Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the mckinstryite belonged to the mineral class of "sulfides and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 brodtkorbite , eukairite , henryite , imiterite , jalpait , selenojalpait and stromeyerite, it formed the unnamed group II / B.06 .

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 mckinstryite to the class of "sulfides and sulfosalts" and there in the department of "metal sulfides, M: S> 1: 1 (mainly 2: 1) ”. However, this is further subdivided according to the predominant metals in the compound, so that the mineral can be found according to its composition in the sub-section "with copper (Cu), silver (Ag), gold (Au)", where the unnamed member is the only member Forms group 2.BA.25b .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns mckinstryite to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here he is to be found as the only member of the unnamed group 02.04.05 within the subsection “ Sulphides - including selenides and tellurides - with the composition A m B n X p , with (m + n): p = 2: 1 ”.

Education and Locations

Mckinstryite forms under hydrothermal conditions at temperatures below 94.4 ° C, as it is no longer stable above this. As accompanying minerals may vary by locality actinolite , aragonite , arsenopyrite , Balkanit , barite native bismuth , bornite , calcite , chalcocite , chalcopyrite , cinnabar , djurleite , Digenite , pyrite , rammelsbergite , native silver, silver amalgam , Stromeyerite , Tennantit and Wittichenite occur.

As a rare mineral formation, mckinstryite could only be detected at a few sites, whereby so far (as of 2013) around 40 sites are known. In addition to the type locality "Foster Mine" and the nearby "Silverfields Mine" in Ontario, the mineral occurred in Canada in the "Echo Bay Mine" and the area around Port Radium on Great Bear Lake in the Northwest Territories.

In Germany, mckinstryite is so far only known from the Clara mine near Oberwolfach in Baden-Württemberg and from the Silberhütte near Altenau in Lower Saxony and the only known site in Austria so far is the Schwarzleograben near Hütten in the Salzburg municipality of Leogang .

Other previously known sites include:

Europe

Africa

Asia

Australia and Oceania

North and South America

Crystal structure

Mckinstryite crystallizes orthorhombically in the space group Pnma with the lattice parameters a = 14.047  Å , b = 7.805 Å and c = 15.691 Å as well as 8 formula units per unit cell .

See also

literature

  • Uwe Kolitsch: The crystal structure and compositional range of mckinstryite. In: Mineralogical Magazine. February 2010, Volume 74 (1), pp. 73–84 ( PDF 1.16 MB )

Web links

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

Individual evidence

  1. ↑ a b c d Uwe Kolitsch: The crystal structure and compositional range of mckinstryite. In: Mineralogical Magazine. February 2010, Volume 74 (1), pp. 73–84 ( PDF 1.16 MB )
  2. ↑ Mindat - Mckinstryite
  3. ↑ IMA / CNMNC List of Mineral Names - Mckinstryite (PDF 1.5 MB)
  4. ↑ Webmineral - Mckinstryite
  5. ↑ a b Mckinstryite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 62.8 kB )
  6. ↑ Mindat - Number of localities for Mckinstryit
  7. ↑ Find location list for Mckinstryite at the Mineralienatlas and at Mindat