Barbosalith
| Barbosalith | |
|---|---|
 |
|
| General and classification | |
| chemical formula | Fe 2+ Fe 2 3+ [(OH) 2 | (PO 4 ) 2 ] |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.BB.40 ( 8th edition : VII / B.08) 41.10.01.04 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic 2 / m |
| Room group (no.) | P 2 1 / c (No. 14) |
| Lattice parameters |
a = 7.25 Å ; b = 7.46 Å; c = 7.49 Å β = 120.2 ° |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 6th |
| Density (g / cm 3 ) | measured: 3.60 to 3.62; calculated: 3.71 |
| Cleavage | is missing |
| Break ; Tenacity | clamshell; brittle |
| colour | dark blue, blue-green, greenish-black, black |
| Line color | dark blue |
| transparency | translucent to almost opaque |
| shine | Glass gloss to earthy matt |
| Crystal optics | |
| Refractive indices |
n α = 1.760 to 1.780 n β = 1.770 to 1.810 n γ = 1.835 to 1.840 |
| Birefringence | δ = 0.075 |
| Optical character | biaxial positive |
| Axis angle | 2V = measured: 64 to 70 ° |
| Pleochroism | visible: X = Y = dark blue-green; Z = dark olive green |
Barbosalith is a rarely occurring mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition Fe 2+ Fe 2 3+ [(OH) 2 | (PO 4 ) 2 ] and thus represents the iron analog of scorzalite (Fe 2+ Al 2 [(OH) 2 | ( PO 4 ) 2 ]).
Barbosalith is translucent to almost opaque and usually only develops microcrystalline mineral aggregates or crusty coatings, but rarely also sturdy, prismatic and pseudotetragonal or cubic crystals up to about 0.25 mm in size with a dark blue, blue-green, greenish-black or black color with a dark blue line color .
Special properties
Barbosalith releases water in a closed tube. The mineral is relatively resistant to acids, i.e. it dissolves slowly in hot, dilute hydrochloric acid (HCl) and not at all in dilute nitric acid (HNO 3 ). Barbosalith also only reacts slowly with alkaline solutions; it is only attacked by the so-called Clerici solution , a fluid used to measure the density of minerals.
Etymology and history
Barbosalith was first described in the "Sapucaia Mine" near Sapucaia do Norte ( Galiléia ) in the Brazilian state of Minas Gerais and in 1955 by Marie Luise Lindberg (-Smith, * 1918) and William Thomas Pecora (1913–1972), who named the mineral after Brazilian geologist Aluízio Licínio de Miranda Barbosa (* 1916).
classification
In the meanwhile outdated, but still in use 8th edition of the mineral classification according to Strunz , the Barbosalith belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates with foreign anions ", where it belongs together with Hentschelit , Lazulith , Lipscombit , Scorzalith , Richellit , Trolleit , Wilhelmkleinit and Zinklipscombit the " Lazulite group" with the system no. VII / B.08 .
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 the Barbosalith 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 other anions (OH etc.) to the phosphate, arsenate or vanadate complex (RO 4 ), so that the mineral according to its composition in the sub-section “With exclusively medium-sized cations; (OH etc.): RO 4 ≤ 1: 1 "can be found, where the still existing" lazulite group "with the system no. Can only be found together with Hentschelite, Lazulith, Scorzalith and Wilhelmkleinite. 8.BB.40 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Barbosalith to the class of "phosphates, arsenates and vanadates" and there in the category of "anhydrous phosphates, etc., with hydroxyl or halogen". Here he is together with Lazulith, Scorzalith and Hentschelit in the "Lazulithgruppe" with the system no. 41.10.01 within the subsection of " Anhydrous phosphates etc., with hydroxyl or halogen with (A 2+ B 2+ ) 3 (XO 4 ) 2 Z q ".
Modifications and varieties
The compound Fe 2+ Fe 2 3+ [(OH) 2 | (PO 4 ) 2 ] is dimorphic , so it occurs naturally as a tetragonally crystallizing lip combit in addition to the monoclinically crystallizing barbosalite .
Education and Locations
Barbosalite is a secondary mineral and is formed from primary phosphates through the oxidation and addition of hydroxide ions in complex granitic pegmatites , where it is mostly found in paragenesis with tavorite , but also with hureaulite , heterosite , triphyline , vivianite , roscherite and rockbridgeite .
As a rare mineral formation, Barbosalith could only be proven at a few sites, whereby so far (as of 2013) around 40 sites are known. In addition to its type locality "Sapucaia Mine" in Galiléia, the mineral appeared in Brazil in the communities of Água Boa , Conselheiro Pena and Mendes Pimentel in Minas Gerais and at Pedra Lavrada in Paraíba .
In Germany, Barbosalith has so far only been found in the Upper Palatinate Forest , more precisely at Kreuzberg near Pleystein , in the “Cornelia pit” near Hagendorf ( Weidhaus ) and in the pegmatite outcrop near Althütte ( Waldmünchen ) in Bavaria.
Other locations include Argentina, Australia, France, Madagascar, Morocco, Namibia, Portugal, Rwanda, Spain, South Africa, the Czech Republic, the United Kingdom (UK) and the United States of America (USA).
Crystal structure
Barbosalith crystallizes monoclinically in the space group P 2 1 / c (space group no. 14) with the lattice parameters a = 7.25 Å ; b = 7.46 Å; c = 7.49 Å and β = 120.2 ° as well as 2 formula units per unit cell .
See also
literature
- ML Lindberg, WT Pecora: Tavorite and Barbosalite, two new phosphate minerals from Minas Gerais, Brazil, In: American Mineralogist. Volume 40 (1955), pp. 952–966 (English, PDF 989.8 kB ; detailed description of Barbosalith from p. 5 of the PDF file)
Web links
- Mineral Atlas: Barbosalith (Wiki)
Individual evidence
- ↑ a b c d e f 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. 445 .
- ↑ Webmineral - Barbosalite (English)
- ↑ a b c Barbosalite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 64.4 kB )
- ↑ a b c d Mindat - Barbosalite (English)
- ^ ML Lindberg, WT Pecora: Tavorite and Barbosalite, two new phosphate minerals from Minas Gerais, Brazil, In: American Mineralogist. Volume 40 (1955), p. 959 (English, PDF 989.8 kB ; p. 8)
- ^ Daniel Atencio, José MV Coutinho, Stefan Graeser, Paulo A. Matioli, Luiz AD Menezes Filho: Lindbergite, a new Mn oxalate dihydrate from Boca Rica mine, Galiléia, Minas Gerais, Brazil, and other occurrences. In: American Mineralogist. 2004, Volume 89, pp. 1087-1091 ( PDF 1.4 MB )
- ^ Charles A. Anderson: William Thomas Pecora 1913-1972 , National Academy of Sciences, Washington DC 1975 ( PDF )
- ↑ Mindat - Number of localities for Barbosalith
- ↑ Find location list for Barbosalith at the Mineralienatlas and at Mindat