Brandholzite

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Brandholzite
Brandholzite.jpg
Brandholzite from the Kriznica mine in Pernek , Bratislavský kraj , Slovenia
General and classification
other names

IMA 1998-017

chemical formula MgSb 2 5+ (OH) 12 • 6H 2 O
Mineral class
(and possibly department) 		Oxides and hydroxides
System no. to Strunz
and to Dana 		4.FH.05
06.03.09.02
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol trigonal-pyramidal; 3
Space group P 3 (No. 143)Template: room group / 143
Lattice parameters a  = 16.12  Å ; c  = 9.87 Å
Formula units Z  = 6
Twinning after {10 1 0}
Physical Properties
Mohs hardness 2 to 3
Density (g / cm 3 ) 2.65
Cleavage no
Break ; Tenacity shell-like, brittle
colour colorless, milky white
Line color White
transparency transparent
shine Glass gloss
Crystal optics
Refractive indices n ω  = 1.570
n ε  = 1.569
Birefringence δ = 0.001
Optical character uniaxial negative

Brandholzite is a very rarely occurring mineral from the mineral class of " oxides and hydroxides " with the chemical composition MgSb 2 5+ (OH) 12 · 6H 2 O and is therefore chemically a water-containing magnesium - antimony- hydroxide.

Brandholzite crystallizes in the trigonal crystal system and develops mostly transparent, colorless to milky white, tabular crystals up to about 1 mm in size in rosette-shaped aggregates .

Etymology and history

Was discovered for the first time as a new mineral substance recognized in 1998 by the amateur collector Stefan Meier in gold - antimony - quartz - veins of the former Mining District of Brandholz- Goldkronach in German Fichtelgebirge . It is named after this type of locality .

It was analyzed and scientifically described by Alexandra Friedrich , Manfred Wildner , Ekkehart Tillmanns and Peter L. Merz , who submitted their results and the chosen name to the International Mineralogical Association (IMA) for examination of the mineral status. It was recognized as an independent mineral under the name Brandholzit in the same year under application number IMA 1998-017 . The results of the investigation and the recognized name were published in the American Mineralogist in 2000 .

classification

Since the brandholzite was only recognized as an independent mineral in 1998, it is not yet listed in the 8th edition of the Strunz mineral classification, which has been outdated since 1977 . Only in the Lapis mineral directory , which was revised and updated in 2018 by Stefan Weiß, which is still based on this classic system from Karl Hugo Strunz out of consideration for private collectors and institutional collections , the mineral received the system and mineral number. IV / F.04-15 . In the "lapis system" this corresponds to the class of "oxides and hydroxides" and there the department "hydroxides and oxidic hydrates (water-containing oxides with layered structure)", where fireholzite together with bottinoite forms an independent but unnamed group.

The 9th edition of Strunz's mineral systematics , valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, also assigns brandholzite to the class of “oxides and hydroxides”, but in the category of “hydroxides (without V or U) ”. This is further subdivided according to the possible presence of further hydroxide ions and / or crystal water as well as the crystal structure, so that the mineral according to its composition and structure in the sub-section “Hydroxides with H 2 O ± (OH); isolated octahedron ”can be found, where together with bottinoite it forms the unnamed group 4.FH.05 .

The systematics of minerals according to Dana also assigns brandholzite to the class of "oxides and hydroxides" and there into the category of "hydroxides and hydroxides containing oxides". Here it can be found together with Bottinoit in the unnamed group 06.03.09 within the sub-section "Hydroxides and hydroxide-containing oxides with (OH) 3 or (OH) 6 groups".

Crystal structure

Brandholzite crystallizes isotypically with bottinoite in the trigonal crystal system in the space group P 3 (space group no. 143) with the lattice parameters a  = 16.12  Å and c  = 9.87 Å as well as 6 formula units per unit cell . Template: room group / 143

Education and Locations

Brandholzit formed secondarily by weathering of stibnite and therefore is also found mostly in paragenesis with this and with antimony - ocher .

Apart from its type locality Brandholz-Goldkronach, the mineral has so far (as of 2010) only been found in the antimony mine near Goesdorf in Luxembourg and in the Krížnica mine in the Little Carpathians in Bratislava, Slovakia.

See also

literature

  • Alexandra Friedrich, Manfred Wildner, Ekkehart Tillmanns, Peter L. Merz: Crystal chemistry of the new mineral brandholzite, Mg (H 2 O) 6 [Sb (OH) 6 ] 2 , and of the synthetic analogues M 2+ (H 2 O ) 6 [Sb (OH) 6 ] 2 (M 2+ = Mg, Co) . In: American Mineralogist . tape 85 , 2000, pp. 593-599 (English, rruff.info [PDF; 357 kB ; accessed on September 25, 2019]).

Web links

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

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  728 (English).
  2. ↑ David Barthelmy: Brandholzite Mineral Data. In: webmineral.com. Retrieved September 25, 2019 .
  3. ↑ a b c d Brandholzite. In: mindat.org. Hudson Institute of Mineralogy, accessed September 25, 2019 .
  4. ^ The Mineral Cabinet Stefan Meier / Marktredwitz - Minerals from the Fichtel Mountains. In: fichtelgebirgs-mineralien.de. October 7, 2018, accessed September 25, 2019 .
  5. ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
  6. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1.7 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed September 25, 2019 .