Schlemait

Schlemait
General and classification
other names	IMA 2003-026
chemical formula	(Cu, □) 6 (Pb, Bi) Se 4
Mineral class; (and possibly department)	Sulfides and sulfosalts
System no. to Strunz ; and to Dana	2.BE.25 ; 02.16.12.02
Crystallographic Data
Crystal system	monoclinic
Crystal class ; symbol	monoclinic prismatic; 2 / m
Space group	P 2 1 / m (No. 11)
Lattice parameters	a = 9.564 Å ; b = 4.100 Å; c = 10.255 Å ; β = 100.07 °
Formula units	Z = 2
Physical Properties
Mohs hardness	3, Vickers hardness VHN 25 = 106 kg / mm 2
Density (g / cm 3 )	7.54 (calculated)
Cleavage	is missing
Break ; Tenacity	uneven; brittle
colour	black
Line color	black
transparency	opaque (opaque)
shine	Metallic luster

Schlemait , is a very rarely occurring mineral from the mineral class of " sulfides and sulfosalts " with the chemical formula (Cu, □) ₆ (Pb, Bi) Se ₄ . Chemically speaking, Schlemait is thus a copper-lead-bismuth-selenide, which is structurally related to the sulfides.

Schlemait crystallizes in the monoclinic crystal system and develops exclusively xenomorphic to subidiomorphic aggregates as well as isolated subidiomorphic crystals up to a few hundred micrometers in size. Well-formed crystals are unknown.

Etymology and history

Shaft headframe of shaft 371 - the main shaft of the Niederschlema-Alberoda deposit, which provided the name for the mineral Schlemait

Schlemait was discovered during the survey of ore sections of Se-containing minerals from the uranium deposit Niederschlema-Alberoda and was discovered in 2003 by an international research team with Hans-Jürgen Förster, Mark A. Cooper, Andrew C. Roberts, Chris J. Stanley, Alan J. Criddle, Frank C. Hawthorne, JH Gilles Laflamme and Gerhard Tischendorf. The material from which the bevel was made had already been found in 1964.

The mineral was recognized by the International Mineralogical Association (IMA) in 2003 and named after its type locality, the Schlema-Alberoda ore field in the former mining region in Saxony, Germany.

Type material of the mineral is in the Mineralogical Institute of the Technical University Bergakademie Freiberg in Germany (No. 80824), in the Natural History Museum , London , (Catalog No. BM 2003,4), as well as in the Systematic Reference Series of the National Mineral Collection of Canada, Geological Survey of Canada in Ottawa , (Catalog No. 68099).

classification

Since the Schlemait was only recognized as an independent mineral in 2003, it is not listed in the Strunz mineral system (8th edition), which has been outdated since 2001 .

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 Schlemait 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 lead (Pb), bismuth (Bi)", where it is the only member of the unnamed group 2.BE .25 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Schlemait to the class of "sulfides and sulfosalts" and there in the department of "sulfide minerals". Here it can be found together with Furutobeit in the unnamed group 02.16.12 within the sub-section " Systematics of minerals according to Dana / Sulphides # 02.16 Sulphides - including selenides and tellurides - with various formulas ".

Crystal structure

Schlemait crystallizes in the monoclinic crystal system in the space group P 2 ₁ / m (space group no. 11) with the lattice parameters a = 9.564 Å ; b = 4.100 Å; c = 10.255 Å and β = 100.07 °; as well as two formula units per unit cell . Template: room group / 11

Structural relationships to the chemically similar mineral furutobeit, (Cu, Ag) ₆ PbS ₄ , are believed to be probable, but both minerals are not isostructural. Schlemait is therefore not the Se analogue of Furutobeit.

properties

morphology

Schlemait is never found in clear crystals, but exclusively in the form of xenomorphic to subidiomorphic adhesions with other selenides in aggregates up to several hundred micrometers in size. Furthermore, isolated subidiomorphic crystals of the same size were also observed. Schlemait forms nest-like accumulations with the other selenide minerals with a diameter of 2 to 5 cm.

physical and chemical properties

The aggregates of the Schlemait are black, the line color of the shiny metal Schlemait is also described as black. Schlemait is brittle, has an uneven break and no cleavage. With a Mohs hardness of 3, Schlemait is one of the soft to medium-hard minerals that, like the reference mineral calcite, can be scratched with a copper coin. The calculated density of the mineral is 7.54 g / cm ³ .

In the reflected light (bevel), Schlemait is gray, shows a very weak bireflectance and no pleochroism. Compared to the relatively blue berzelianite , the white clausthalite and the beige eukairite , however, Schlemait appears pale pink. With crossed polars, the mineral shows very weak anisotropy with rotational colors in very pale metallic orange and blue shades.

Education and Locations

Schlemait is found on hydrothermal , selenium-rich veins. It is associated with Clausthalite , Eukairite , Berzelianite and Löllingite in a matrix of dolomite - anchorite . In another ore section, in addition to this paragenesis , Tiemannite , Umangite and Bohdanowiczite could be observed. The selenides form nests and crevice fillings in dolomite anchorite (calcite) veins of the mgu formation (magnesium carbonate pitchblende formation) as well as finely distributed grains in the intergranular cavities of the Mg-Fe carbonates.

So far (as of 2016) the mineral could only be detected at its type locality, the shaft 371 (ore vein "Tiber" on the -855 m level, block 5128) in the deposit area Niederschlema-Alberoda near Hartenstein ( Saxony ). Of the three uranium ore deposits in the Erzdistrikt Schneeberg-Schlema-Alberoda (i.e. Schneeberg sensu stricto, Oberschlema and Niederschlema-Alberoda), Niederschlema-Alberoda is considered to be the most important occurrence of selenides in the Ore Mountains.

use

Schlemait with end link composition (Cu ₆ PbSe ₄ ) consists of about 42% copper, about 23% lead and about 35% selenium; the bismuth end link (Cu ₅ BiSe ₄ ), which has not yet been detected in nature, consists of about 38% copper, about 25% bismuth and about 37% selenium. Due to its rarity, however, Schlemait is technically completely insignificant as a raw material for these elements.

literature

Hans-Jürgen Förster, Mark A. Cooper, Andrew C. Roberts, Chris J. Stanley, Alan J. Criddle, Frank C. Hawthorne, JH Gilles Laflamme, Gerhard Tischendorf (2003): Schlemaite, (Cu, □) ₆ (Pb , Bi) Se ₄ , a new mineral species from Niederschlema-Alberoda, Erzgebirge, Germany: Description and crystal structure In: Canadian Mineralogist , Volume 41, 1433–1444 ( PDF, 511 kB ).
Schlemaite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF, 95.4 kB )

Web links

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r Hans-Jürgen Förster, Mark A. Cooper, Andrew C. Roberts, Chris J. Stanley, Alan J. Criddle, Frank C. Hawthorne, JH Gilles Laflamme, Gerhard Tischendorf (2003): Schlemaite, (Cu, □) ₆ (Pb, Bi) Se ₄ , a new mineral species from Niederschlema-Alberoda, Erzgebirge, Germany: Description and crystal structure In: Canadian Mineralogist , Volume 41, 1433-1444 ( PDF, 511 kB ).

[Foerster-1] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r Hans-Jürgen Förster, Mark A. Cooper, Andrew C. Roberts, Chris J. Stanley, Alan J. Criddle, Frank C. Hawthorne, JH Gilles Laflamme, Gerhard Tischendorf (2003): Schlemaite, (Cu, □) ₆ (Pb, Bi) Se ₄ , a new mineral species from Niederschlema-Alberoda, Erzgebirge, Germany: Description and crystal structure In: Canadian Mineralogist , Volume 41, 1433-1444 ( PDF, 511 kB ).