Baumhauerite

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Baumhauerite
Baumhauerite-177525.jpg
Baumhauerite, place of discovery: Binntal
General and classification
other names

IMA 1988-061

chemical formula
  • Pb 3 As 4 S 9
  • Oxide formula: 3 PbS · 2 As 2 S 3
Mineral class
(and possibly department) 		Sulfides and sulfosalts
System no. to Strunz
and to Dana 		2.HC.05 ( 8th edition : II / E.24)
03.06.13.01
Similar minerals Baumhauerit-2a
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triclinic pinacoidal; 1
Room group (no.) P 1 (No. 2)
Lattice parameters a  = 22.80  Å ; b  = 8.36 Å; c  = 7.89 Å
α  = 90 °; β  = 97.3 °; γ  = 89.9 °
Formula units Z  = 4
Twinning very often twin lamellas parallel (100)
Physical Properties
Mohs hardness 3
Density (g / cm 3 ) measured: 5.33 to 5.44; calculated: [5.42]
Cleavage according to the dominant area (100)
Break ; Tenacity shell-like
colour lead gray to steel gray
Line color chocolate brown
transparency opaque
shine fresh crystals: strong metallic sheen
Other properties
Special features often rounded edges

Baumhauerite is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the triclinic crystal system with the chemical composition Pb 3 As 4 S 9 , so from a chemical point of view it is a complex lead - arsenic sulfide, which is counted among the sulfosalts.

Baumhauerite is opaque in every form and usually only develops small, prismatic to tabular and striped crystals , but also granular mineral aggregates of lead to steel-gray color with a chocolate-brown streak color . Fresh samples have a strong metallic luster . Unprotected, however, the crystal surfaces become iridescent in bright colors after a while.

Etymology and history

Baumhauerite was first discovered in the Lengenbach / Binntal mine in the Swiss canton of Valais and described in 1902 by RH Solly, who named the mineral after Heinrich Adolph Baumhauer (1848-1926), Professor of Mineralogy at the University of Friborg (Switzerland) .

In 1903, the Natural History Museum Vienna bought a piece of fused Baumhauerite crystals measuring 6 × 2.5 × 2.3 cm. Nowadays, even crystals one centimeter in size are decent finds.

classification

In the now outdated, but still in use 8th edition of the mineral classification according to Strunz , Baumhauerite belonged to the mineral class of "sulfides and sulfosalts" and there to the department of "sulfosalts", where together with Baumhauerit-2a and Robinsonite it belongs to the unnamed group II / E .24 made.

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 Baumhauerite to the class of "sulfides and sulfosalts", but in the newly defined department of "sulfosalts with SnS as a model " a. This section is further subdivided according to the metals predominating in the compound, so that the mineral can be found according to its composition in the sub-section "Only with lead (Pb)", where it is found together with Baumhauerit-2a and Baumhauerit II (with previously questionable status) the "Baumhauerit-Gruppe" with the system no. 2.HC.05b forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Baumhauerite to the class of "sulfides and sulfosalts" and there in the department of "sulfosalts". Here it is together with Baumhauerit-2a in the unnamed group 06/03/13 within the subsection “ Sulphosalts with the ratio 2.0 <z / y <2.49 and the composition (A + ) i (A 2+ ) j [B y C z ], A = metals, B = semi-metals, C = non-metals ”.

Crystal structure

Baumhauerite crystallizes triclinic in the space group P 1 (space group no. 2) with the lattice parameters a  = 22.80  Å ; b  = 8.36 Å; c  = 7.89 Å; α = 90 °; β = 97.3 ° and γ = 89.9 ° as well as 4 formula units per unit cell .

Education and Locations

Baumhauerite embedded in dolomite from the type locality Lengenbach, Binntal, Switzerland ( total size of the sample: 8.0 × 4.0 × 4.5 cm)

Baumhauerite forms hydrothermally in dolomite rock . In addition to dolomite and tree skin-2a, various lead sulpharsenides, pyrite and realgar occur as accompanying minerals .

As a rare mineral formation, Baumhauerite has so far (as of 2012) only been detected at a few sites. About 15 localities are considered to be known, the type locality Lengenbach in Binn the only known location in Switzerland. However, this site is also known for its rich finds of well-formed crystals up to 2.5 cm in diameter.

In Austria, the mineral has so far appeared in the gypsum mine near Moosegg / Lauperswil (Salzburg) and possibly also in the Haringgraben in the municipality of Oberort- Tragöß (Styria).

Other sites include the “Beltana Mine” near Puttapa in the Australian mountain range known as the Flinders Range, Huntingdon and Marathon in the Canadian province of Ontario, the “Zareh Shuran Mine” in the Iranian province of West Azerbaijan , the “Okoppe Mine” on the Japanese Shimokita peninsula , the antimony-mercury deposit Khaidarkan (Chaidarkan) in the Ferghana Valley in Kyrgyzstan and in the "Perseverance Mine" in the Yukon-Koyukuk Census Area (Alaska), the "Zuni Mine" (Zuñi Mine) on Anvil Mountain (Colorado) , near Sterling Hill (New Jersey) and the Keystone Mine near Birmingham (Pennsylvania) .

See also

literature

Web links

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

Individual evidence

  1. ^ A b c Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  134 .
  2. ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 299 .
  3. ↑ a b c Webmineral - Treetopperite
  4. ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1979, ISBN 3-342-00288-3 , p.  352 .
  5. ↑ a b John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Baumhauerite , in: Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64KB )
  6. ↑ Mindat - Number of known locations for Baumhauerite
  7. ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 59 ( Dörfler Natur ).
  8. Jump up ↑ Mindat - examples of Baumhauerite finds from the Lengenbach mine
  9. ↑ a b Mindat - Treetop Lite