Brendelite
| Brendelite | |
|---|---|
 |
|
| General and classification | |
| other names |
IMA 1997-001 |
| chemical formula |
|
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.BM.15 ( 8th edition : VII / B.37) 03.41.08.02 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / m (No. 12) |
| Lattice parameters |
a = 12.278 Å ; b = 3.815 Å; c = 6.899 Å β = 111.14 ° |
| Formula units | Z = 2 |
| Frequent crystal faces | { 2 01}, {001}, {010}, {100} |
| Physical Properties | |
| Mohs hardness | 4.5, Vickers hardness VHN 15 = 300 ± 30 kg / mm 2 |
| Density (g / cm 3 ) | 6.83 (calculated) |
| Cleavage | no |
| Break ; Tenacity | not specified; not specified |
| colour | black to dark brown or brownish yellow |
| Line color | light brown |
| transparency | opaque, translucent in splinters and small crystals |
| shine | Glass to diamond gloss |
| Crystal optics | |
| Refractive indices |
n α = 2.06 n β = 2.15 n γ = 2.19 |
| Birefringence | δ = 0.13 |
| Optical character | biaxial negative |
| Axis angle | 2V = 70 ° |
| Pleochroism | strong from X = light brown to brown to Y = Z = dark brown to opaque |
| Other properties | |
| Chemical behavior | Completely soluble in warm dilute HCl and without effervescence |
Brendelite is a very rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical formula (Bi, Pb) 2 Fe 3 +, 2 + O 2 (OH) (PO 4 ), so chemically speaking it is a hydrous bismuth - lead - iron phosphate with additional oxygen and hydroxide ions . The components bismuth and lead indicated in round brackets can represent each other in the formula ( substitution , diadochie), but are always in the same proportion to the other components of the mineral.
Brendelite forms idiomorphic crystals up to 0.3 mm in size, tabular according to { 2 01} , which come together to form aggregates up to 3 mm in size . Depending on their size, they are dark brown and translucent or black and opaque. Brendelit is a typical secondary mineral extending through weathering primary ore minerals formed and two on the Halden bismuth cobalt - nickel - silver - deposits has been found.
Etymology and history
.JPG)
During the investigation of secondary minerals in the deposit area of Schneeberg in Saxony, a mineral was found in the area of the former Güldener Falk mine, which, due to its appearance, was originally thought to be atelestite . In detailed X-ray diffractometric and microchemical investigations, however, this phase turned out to be a new mineral that is chemically related to the Paulkellerite , which is also found in Schneeberg . The mineral was recognized in 1997 under the number 97-001 by the International Mineralogical Association (IMA) and in 1989 by a team of German-Austrian scientists led by Werner Krause and Heinz-Jürgen Bernhardt from the Ruhr University Bochum , Catherine McCammon from the Bavarian Geoinstitut and Herta Effenberger from the University of Vienna was first described as Brendelit.
Brendelit was named after Christian Friedrich Brendel (1776–1861), who had been "Machine Director" since 1817 and thus the highest machine officer in Saxon ore mining and had a seat and vote in all Saxon mining authorities, from 1846 also as a mining authority in the Oberbergamt. Brendel's work led to immense progress in Saxon mining. He designed and built four water column machines , introduced the steam engine into Freiberg's mining industry and planned the largest Saxon hut blower at the time for the Antonshütte , which has been preserved as a Schwarzenberg blower in Freiberg. In this way Brendel became one of the most famous citizens of his hometown Schneeberg-Neustädtel.
The type material for brendelite (holotype) comes from the Schneeberg collector Fritz Schlegel and is included in the collection of the Museum of Mineralogy and Geology Dresden in the Museum Association Senckenberg Natural History Collections Dresden under catalog no. Min 17919 Sa (MMG Dresden) kept.
classification
Already in the now outdated, but still in use 8th edition of the mineral classification according to Strunz , the brendelite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates, with foreign anions F, Cl, O, OH", where he together with Cobaltneustädtelit , Neustädtelit , Medenbachit and Paulkellerit the unnamed group VII / B.37 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 brendelite to the category of “phosphates etc. with additional anions; without H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of the additional anions (OH etc.) to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral can be classified in the sub-section “With medium-sized and large cations; (OH etc.): RO 4 = 4: 1 “is to be found where the unnamed group with the system no. 8.BM.15 forms.
The systematics of minerals according to Dana , which is common in the English-speaking world , also assigns brendelite to the class of phosphates, arsenates and vanadates and there in the category of "anhydrous phosphates etc., with hydroxyl or halogen". Here it can be found together with Paulkellerit in the unnamed group 41.03.08 within the subdivision of "Anhydrous phosphates etc., with hydroxyl or halogen and the general formula (AB) 3 (XO 4 ) Z q ".
Chemism
Brendelite has (based on 7 oxygen atoms per formula) the measured composition (Bi 1.27 Pb 0.74 ) Σ = 2.01 (Fe 3+ 0.74 Fe 2+ 0.27 ) Σ = 1.01 [O 2.00 (OH) 1.00 )] Σ = 3.00 · [(PO 4 ) 0.95 (AsO 4 ) 0.02 (VO 4 ) 0.02 ] Σ≈0.99 , resulting in (Bi , Pb) 2 Fe 3 +, 2 + O 2 (OH) (PO 4 ) was idealized and contents of 56.54% Bi 2 O 3 , 18.05% PbO, 5.81% FeO, 6.46% Fe 2 O 3 , 10.91% P 2 O 5 , 0.19% As 2 O 5 , 0.59% V 2 O 5, and 1.46% H 2 O requires.
Since the atoms of bismuth and lead sit in only one crystallographic position, brendelite is a bismuth-rich member of a mixed crystal row between a still hypothetical bismuth end link and a likewise still hypothetical lead end link. The Bi: Pb ratios of the brendelite vary between 1.23: 0.77 and 1.59: 0.41.
The general formula for brendelite contains uncertainties, since the mixed crystal formation with the two heterovalent ions Bi 3+ and Pb 2+ requires a mechanism for charge equalization that has not yet been determined experimentally. Different Bi: Pb ratios can be balanced out either by varying the Fe 3+ : Fe 2+ ratio or by varying the O: OH ratio. Structural studies indicate that at most one hydrogen bond per formula unit is possible, which leads to the general formula (Bi 2 − x Pb x ) Σ = 2 (Fe 3+ 0.78 Fe 2+ 0.22 ) Σ = 1 O 2.78 − x (OH) 0.22 + x (PO 4 ) with 0 <x <0.78 and the two limit compositions (Bi 1.22 Pb 0.78 ) (Fe 3+ 0.78 Fe 2+ 0.22 ) O 2 (OH) (PO 4 ) and Bi 2.00 (Fe 3+ 0.78 Fe 2+ 0.22 ) O 2.78 (OH) 0.22 (PO 4 ) for x = 0.78 or x = 0 leads.
Chemically related to brendelite are Paulkellerite, Bi 2 Fe 3+ O 2 (OH) 2 (PO 4 ), and Zaïrit , Bi (Fe 3+ , Al) 3 (OH) 6 (PO 4 ). Brendelite, Paulkellerit and Zaïrit have remained the only Bi-Fe-Phosphate minerals to this day.
Crystal structure
Brendelite crystallizes in the monoclinic crystal system in the space group C 2 / m (space group no. 12) with the lattice parameters a = 12.278 Å ; b = 3.815 Å; c = 6.899 Å and β = 111.14 ° as well as two formula units per unit cell .
Structural studies were carried out based on single crystal X-ray data, whereby an average structure showing positional disorder of the phosphate group and the hydroxyl group was obtained. By doubling the cell parameter b, an ordered structural model can be derived.
The crystal structure of Brendelits consists of FeO 6 - octahedra ; PO 4 - tetrahedra ; Fe 2 (O o ) 4 (O h ) 2 (PO 4 ) 2 chains parallel [010], which are formed by linking the corners of the above. Polyhedra are formed (first type of chains); Hydrogen bonds and edge-sharing (Bi, Pb) [1 + 4] O 5 polyhedra that form (Bi, Pb) 2 (O o ) 2 (O p ) 2 chains in parallel [010] (second type of chain). The chains of the first type correspond to the M [6] T [4] Φ n chains observed in a variety of phosphates, arsenates, and sulfates . The FeO 6 octahedra and PO 4 tetrahedra are linked by corners to form Fe 2 (O o ) 4 (O h ) 2 (PO 4 ) chains parallel [010] and are connected by hydrogen bonds in (100). Edge-sharing (Bi, Pb) [1 + 4] O 5 polyhedra form (Bi, Pb) 2 (O o ) 2 (O p ) 2 chains parallel to [010]. The chains of the first and second types have common edges and corners.
The atoms of bismuth and lead sit in only one crystallographic position, have a very short bond to one O o atom and are surrounded by two further O o atoms and two O p atoms, which is a [1 + 4] coordination indexed. The (Bi, Pb) [1 + 4] O 5 polyhedra share two O o -O o -and O o -O p edges and form (Bi, Pb) 2 (O o ) 2 (O p ) 2 Chains in [010].
Brendelite is structurally related to Namibite , but because it does not crystallize with the same structure, it is not isotypic or isostructural to Namibite.
properties
morphology
Brendelite always forms grown, idiomorphic crystals up to 0.3 mm in size, which come together to form aggregates of a maximum of 3 mm in size. The crystals are thick tabular after the pinacoid { 2 01} to blocky and also show the surfaces of the pinacoids {001}, {010} and {100}, as the crystal drawing on the right also illustrates. Occasionally there are hemispherical aggregates up to 3 mm in size with a radial structure.
physical and chemical properties
The color of the brendelite is dark brown to black or brown-yellow, depending on the size of its crystals, the color of the mineral, on the other hand, is always light brown. The surfaces of the translucent to opaque crystals have a strong glass-like or even diamond-like sheen , which corresponds to the relatively high birefringence of the mineral. In the thin section the mineral shows dark brown shades under the microscope and a strong pleochroism from X = light brown to brown to Y = Z = dark brown to opaque.
No cleavage was found in the crystals of the brendelite . Information on breakage and tenacity is lacking. Brendelite has a Vickers hardness of VHN 15 = 300 ± 30 kg / mm 2 , which corresponds to a Mohs hardness of 4.5. Brendelite is one of the medium-hard minerals that, like the reference minerals fluorite and apatite, can be scratched more or less easily with a pocket knife. The calculated density for the mineral is 6.83 g / cm³.
Brendelite dissolves completely in warm, dilute hydrochloric acid and does not fizzle out.
Education and Locations
Brendelite arises as a secondary formation in the area of the mineralization of the so-called five-element formation BiCoNiAgU. Bismuth, lead and iron come from the decomposition of former ore minerals. Typically, the mineral sits on thin crusts of tiny eulytin crystals. Other accompanying minerals are bismuthite and bismuth ferrite as well as solid bismuth and quartz .
As a very rare mineral formation, Brendelite could so far (as of 2016) only be described by its type locality and one other location. The type locality is the “Güldener Falk” mine near Schneeberg on the edge of the Schneeberg-Neustädtel cobalt field, Erzgebirgskreis , western Ore Mountains , Saxony , Germany . According to the Schneeberg Chronicle, this pit was first mentioned in 1515. The associated area including the heaps has been used for agriculture for centuries, so that today no mining tools or ruins belonging to the Güldenen Falk have been preserved.
The second location is also in the Saxon Ore Mountains. This is the "Schaarschacht" near Johanngeorgenstadt in the mining area of the same name. Tiny, prismatic crystals of brownish yellow color sit on velvety goethite .
use
Due to their rarity, specimens with brendelite crystals are only coveted by collectors.
See also
literature
- Brendelite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF, 66 kB )
- Werner Krause, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger: Brendelite, (Bi, Pb) 2 Fe 3 +, 2 + O 2 (OH) (PO 4 ), a new mineral from Schneeberg, Germany: Description and crystal structure . In: Mineralogy and Petrology . tape 63 , 1998, pp. 263-277 , doi : 10.1007 / BF01164154 .
Web links
- Mineral Atlas: Brendelite (Wiki)
- Web mineral - brendelite
- Mindat - Brendelit
- RRUFF Database-of-Raman-spectroscopy - Brendelite
- American-Mineralogist-Crystal-Structure-Database - Brendelite
Individual evidence
- ↑ a b c d e f g h i j k l m n o p q r s Werner Krause, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger: Brendelite, (Bi, Pb) 2 Fe 3 +, 2 + O 2 (OH) (PO 4 ), a new mineral from Schneeberg, Germany: Description and crystal structure . In: Mineralogy and Petrology . tape 63 , 1998, pp. 263-277 , doi : 10.1007 / BF01164154 .
- ^ 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. 465 .
- ↑ a b c Joachim Gröbner, Oliver Grimm, Heiko Zienau: New discoveries of interesting bismuth and uranium minerals at the Schaarschacht, Johanngeorgenstadt, Saxony . In: Lapis . 30 (issue 6), 2005, p. 44-51 .
- ↑ a b Brendelite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF, 66 kB )
- ^ Otfried Wagenbreth : Christian Friedrich Brendel. Life and work of an important engineer in the first half of the 19th century (Freiberg research books; D 221) . 1st edition. TU Bergakademie Freiberg, Freiberg 2006, ISBN 978-3-86012-279-2 , p. 1-258 .
- ↑ Type mineral catalog Germany - storage of the holotype stage Brendelit
- ^ Frank C. Hawthorne: Structural hierarchy in M [6] T [4] Φ n minerals . In: Journal of Crystallography . tape 192 , 1990, pp. 1–52 , doi : 10.1524 / zkri.1990.192.14.1 ( researchgate.net [PDF; 1.9 MB ]).
- ^ Fritz Schlegel: New discoveries from the mountain area Schneeberg / Saxony, 1995–99 (I) . In: Lapis . 25 (Issue 2), 2000, pp. 31-38 .
- ↑ Mindat - Number of localities for Brendelite
- ↑ a b List of places where Brendelite was found in the Mineralienatlas and Mindat