Mallestigit

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Mallestigit
General and classification
other names

IMA 1996-043

chemical formula
  • Pb 3 Sb (SO 4 ) (AsO 4 ) (OH) 6 • 3H 2 O
  • Pb 3 Sb 5+ [(OH) 6 | AsO 4 | SO 4 ] • 3H 2 O
Mineral class
(and possibly department) 		Sulphates (selenates, tellurates, chromates, molybdates, tungstates)
System no. to Strunz
and to Dana 		7.DF.25 ( 8th edition : VI / D.11)
07/31/06/04
Similar minerals Quartz, mimetite
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol hexagonal dipyramidal; 6 / m
Space group P 6 3 / m (No. 176)Template: room group / 176
Lattice parameters a  = 8.938  Å ; c  = 11.098 Å
Formula units Z  = 2
Frequent crystal faces {10 1 0}, {10 1 1}, {0001}
Physical Properties
Mohs hardness 4th
Density (g / cm 3 ) 4.91 (calculated)
Cleavage not observed
Break ; Tenacity splintery; brittle
colour colorless, yellowish, orange
Line color White
transparency translucent to translucent
shine Diamond luster
Crystal optics
Refractive indices n ω  = 1.760
n ε  = 1.801
Birefringence δ = 0.041
Optical character uniaxial positive

Mallestigite is a very rarely occurring mineral from the mineral class of " sulfates , including selenates , tellurates , chromates , molybdates and tungstates ". It crystallizes in the hexagonal crystal system with the chemical formula Pb 3 Sb (SO 4 ) (AsO 4 ) (OH) 6 · 3H 2 O, so it is chemically a water-containing lead - antimony- sulfate-arsenate with additional hydroxide ions .

Mallestigit forms long prismatic, quartz-like crystals up to 5 mm in length, which typically come together to form divergent-rayed, sheaf-shaped or fan-shaped aggregates . The mineral sits together with angelsite, brochantite, langite, linarite and schultenite on weathered ore-containing material from polymetallic non-ferrous metal deposits, which u. a. Contains galena and tetrahedrite. The mallestigite also formed during the alteration of these primary ores.

Etymology and history

The "Mallestiger Mittagskogel" (center), after which the Mallestigit was named

In 1996 Manfred Puttner reported for the first time about a new mineral found on the heaps of the former ore mining of Neufinkenstein-Grabanz on Mallestiger Mittagskogel , which was originally thought to be fleischerite . Also in 1996 a team of Austrian mineralogists with Isabella Sima, Karl Ettinger and Franz Walter from the Karl-Franzenz-University Graz , Brigitte Koppelhuber-Bitschnau from the Technical University Graz and Josef Taucher from the Universalmuseum Joanneum in Graz presented this phase on the MinPet '96, the joint conference of the Swiss Mineralogical and Petrographic Society (SMPG) and the Austrian Mineralogical Society (ÖMG) as a new mineral. After submitting this compound to the IMA, it was recognized as a new mineral under the number "IMA 1996-043" in the same year. In 1998 the first description of the Mallestigite appeared as an "Extended Abstract" in the "Mitteilungen der Österreichische Mineralogische Gesellschaft". Further data was first made available by Franz Walter to Joseph Anthony Mandarino for his column "New Minerals" in the scientific magazine "The Canadian Mineralogist". Isabella Sima named the mineral “Mallestigit” after its type of locality on Mallestiger Mittagskogel.

There is no information on the storage location of the Mallestigit type material .

classification

Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the mallestigite belonged to the mineral class of "sulfates, chromates, molybdates, wolframates" and there to the department of "anhydrous sulfates, with foreign anions ", where it belonged together with Schaurteit , Despujolsit and Fleischerit the Schaurteit group with system no. VI / D.11 formed.

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 mallestigite to the category of "sulfates (selenates, etc.) with additional anions, with H 2 O". This is, however, further subdivided according to the relative size of the cations involved , so that the mineral can be found according to its composition in the sub-section "With large and medium-sized cations" , where, together with Schaurteit, Despujolsite and Fleischerite, the Fleischerite group with the system No. 7.DF.25 forms.

The Dana system of minerals used in the English-speaking world also assigns mallestigite to the class of “sulfates, chromates and molybdates” and there to the “hydrated sulfates with hydroxyl or halogen” class. Here it is together with Despujolsit, Fleischerit and Schaurteit in the Despujolsitgruppe with the system no. 07/31/06 within the subdivision of " Water-containing sulphates with hydroxyl or halogen with (A + B 2+ ) 2 (XO 4 ) Z q  • x (H 2 O) ".

Chemism

Average values ​​from 14 microprobe analyzes on Mallestigit from Mallestiger Mittagskogel resulted in levels of 65.67% PbO 2 , 14.68% Sb 2 O 5 , 9.71% As 2 O 5 , 8.64% SO 3 and 10.38% H 2 O (calculated). This gives the empirical formula Pb 3.06 Sb 0.95 [(SO 4 ) 1.12 (AsO 4 ) 0.88 ] Σ = 2.00 (OH) 5.99 · 3.01H 2 O, which leads to Pb 3 Sb (SO 4 ) (AsO 4 ) (OH) 6 · 3H 2 O can be idealized. The empirical formula agrees well with the crystal chemical formula resulting from the structure refinement [9] Pb 3 [6] Sb [(S 0.95 As 0.05 ) O 4 ] [(As 0.86 S 0.14 ) O 4 ] (OH) 6 · 3H 2 O, the coordination number of the respective position in the crystal structure being indicated in the square brackets .

Crystal structure

Mallestigit crystallizes hexagonally in the space group P 6 3 / m (space group no. 176) with the lattice parameters a  = 8.938  Å and c  = 11.098 Å as well as two formula units per unit cell . Template: room group / 176

The framework of the structure of the Mallestigits form two in the direction of the c-axis [001] superimposed Sb (OH) 6 - octahedron which on Pb 2+ are linked. The angles resulting from the bond lengths Sb – O4 (OH) correspond on average to ideal octahedral angles. Pb is surrounded by four O4 (OH), two O2W, one O3 (T1), one O3 (T2) and one O1 (T2) in an irregular [9] er coordination. The Pb atoms are in one plane with the H 2 O molecules and form a six-membered ring. S and As have a [4] coordination with O and share a fourfold point position. A refinement of the occupation resulted in an S: As ratio close to 1: 1, which also confirmed the chemical analysis. The peak oxygen for As (T1) has no further bond to a cation and is saturated via three strong hydrogen bonds (O1 (T1) –O2 (W) = 2.54 Å).

properties

Costume and habitus of mallestigite crystals
Mallestigit 1.png
long prismatic, quartz-like
Mallestigit 2.png
long prismatic crystal with base pinacoid (same colors represent the same surface shapes)
Mallestigit Szepter.png
scepter-shaped crystal

morphology

Mallestigit forms, according to [001], long prismatic crystals of up to 2 mm in length and 0.4 mm in thickness, which come together to form 3 mm large, divergent-rayed, sheaf-shaped or fan-shaped aggregates. Matted aggregates and single crystals are also common. Mallestigite crystals from the ancient slag of the Juliushütte near Astfeld in the North Harz even reach lengths of up to 5 mm. The shape of the trapezoid is the hexagonal prism {10 1 0}, the end faces are formed either by the hexagonal dipyramid {10 1 1} alone or together with those of the basic pinacoids {0001} (see also the crystal drawings on the right). The pyramids and prism surfaces are sometimes rough, but mostly smooth. Overall, the morphology of mallestigite crystals resembles that of high quartz or mimetite .

physical and chemical properties

Mallestigite crystals are colorless, water-clear or yellowish or orange in color. Their line color , however, is always white. The surfaces of the translucent to transparent crystals have a strong diamond-like sheen , which corresponds well with the very high birefringence of the mineral (δ = 0.041).

No cleavage was found in the mallestigite crystals . Due to its brittleness, the mineral breaks like kainite or kernite , with the fracture surfaces being splintery. Mallestigite has a Vickers hardness of VHN 10  = 176 kg / mm 2 , which corresponds to a Mohs hardness of 4, and is one of the medium-hard minerals that, like the reference mineral fluorite, can be easily scratched with a pocket knife. Measured values ​​for the density of mallestigite do not exist, the calculated density for the mineral is 4.91 g / cm³.

Education and Locations

Mallestigite was found for the first time on heaps of a former Cu-Pb-Zn mine in narrow fissures of a limestone, where it was formed during the weathering of the primary ore minerals galena and tetrahedrite . Lead and antimony come from the decomposition of these former sulfidic ore minerals. As Begleitminerale were Anglesite , Brochantite , Langit , Linarite and Schultenit identified.

As a very rare mineral formation, mallestigite could only be described from five sites so far (status 2016). The type locality of Mallestigit are the heaps of the former Cu-Pb-Zn mining “Neufinkenstein-Grabanz” near Finkenstein , Karawanken , Carinthia , Austria ( coordinates of the heap on Mallestiger Mittagskogel ), 1 km northwest of the “Mallestiger Mittagskogel” .

Two other sites in Austria are the "Gilgenstollen" on the western slope of the Silberberg in the area "Geyer - Silberberg" near Rattenberg , mining district Schwaz - Brixlegg in the Inn Valley , Tyrol , and the former arsenic and gold mining area on the Straßegg Pass near Gasen not far from Birkfeld , Styria .

The second site in the world was the slag deposit of the "Herzog-Julius-Hütte" north of the Granestausees near Astfeld , 3.5 km west-northwest of Goslar , Harz , Lower Saxony , Germany . The dumping of the slag began here as early as 1270, and the smelter was closed in 1868. In the cavities of the slag material, quartz-like mallestigite crystals up to 5 mm long were found, which occasionally have scepter-like thickenings at one end, as the adjacent drawing also shows.

The third site for Mallestigit is the old Cu-Ag mine of the "Miniera di Monte Avanza" near Forni Avoltri , Friuli-Venezia Giulia , Italy . The mallestigite crystals found here are elongated according to [001], colorless to orange in color and up to 2 mm long and 0.5 mm thick. In contrast to the crystals of the type locality, the end faces are mostly formed by the base pinacoid.

use

Mallestigite is only of interest to mineral collectors due to its rarity.

See also

literature

  • Mallestigite . 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; 82 kB ; accessed on January 2, 2018]).
  • Isabella Sima: Mallestigit, Pb 3 Sb (SO 4 ) (AsO 4 ) (OH 6 ) 3H 2 O, a new mineral from a heap of the former Cu-Pb-Zn mining NW of Mallestiger Mittagskogel in the West Karawanken, Carinthia, Austria . In: Communications from the Austrian Mineralogical Society . tape 143 , 1998, pp. 225-227 .

Web links

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

Individual evidence

  1. ↑ a b c d Mallestigite . 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; 82  kB ; accessed on January 2, 2018]).
  2. ↑ a b c d e Günter Schnorrer: Mallestigit, Pb 3 Sb [(OH) 6 | AsO 4 | SO 4 ] · 3H 2 O, another new mineral formation in the ancient slag of the Harz - a second location for this compound and another Proof of formation on both “natural” and “artificial” slag heaps . In: The opening . tape 54 , 2003, p. 42-44 .
  3. ^ A b c d Manfred Puttner: New mineral discoveries from the Neufinkenstein-Grabanz mining industry, Mallestiger Mittagskogel (West Karawanken, Carinthia) . In: The opening . tape 47 , 1996, pp. 186-192 .
  4. ↑ a b c Maurizio Giarduz, Sylvano Iob, Erica Bittarello, Marco E. Ciriotti, Bruno Fassina: Mallestigite di Monte Avanza: terzo ritrovamento mondiale . In: Micro . tape 143 , 2015, p. 54-63 .
  5. ↑ a b c d Isabella Sima, Karl Ettinger, Brigitte Koppelhuber-Bitschnau, Josef Taucher, Franz Walter: Pb 3 Sb (OH) 6 (AsO 4 , SO 4 ) 2 · 3H 2 O, a new mineral isotype with Fleischerite . In: Communications from the Austrian Mineralogical Society . tape 141 , 1996, pp. 224-225 .
  6. ↑ a b Joseph A. Mandarino: New Minerals . In: The Canadian Mineralogist . tape 41 , 2003, p. 1314 , doi : 10.2113 / gscanmin.41.5.1309 ( rruff.info [PDF; 106 kB ]).
  7. ↑ a b c d e f g Isabella Sima: Mallestigit, Pb 3 Sb (SO 4 ) (AsO 4 ) (OH 6 ) 3H 2 O, a new mineral from a dump of the former Cu-Pb-Zn mining in the NW of Mallestiger Mittagskogel in the West Karawanken, Carinthia, Austria . In: Communications from the Austrian Mineralogical Society . tape 143 , 1998, pp. 225-227 .
  8. ↑ a b Mindat - mineral description Mallestigit
  9. ↑ Mindat - Number of localities for Mallestigit
  10. ↑ List of localities for mallestigite in the Mineralienatlas and Mindat