Mounanait
| Mounanait | |
|---|---|
 the type locality "Mounana Mine", Franceville, Haut-Ogooué, Gabon (size: 7 × 4.5 cm) |
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| General and classification | |
| other names |
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| chemical formula |
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Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
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System no. to Strunz and to Dana |
8.CG.15 ( 8th edition : VII / C.31) 10.41.07.01 |
| Crystallographic Data | |
| Crystal system | monoclinic |
| Crystal class ; symbol | monoclinic prismatic; 2 / m |
| Space group | C 2 / m (No. 12) |
| Lattice parameters |
a = 9.294 Å ; b = 6.166 Å; c = 7.713 Å β = 115.57 ° |
| Formula units | Z = 2 |
| Frequent crystal faces | {010} |
| Twinning | often, according to two different laws (rotation twins around [001] or with {1 1 0} as the twin plane ) |
| Physical Properties | |
| Mohs hardness | 4.5 |
| Density (g / cm 3 ) | 4.85 (measured); 4.88-4.89 (calculated) |
| Cleavage | good after {001} |
| Break ; Tenacity | not specified; not specified |
| colour | reddish brown |
| Line color | probably light brown |
| transparency | translucent to translucent |
| shine | Diamond luster (according to refractive index) |
| Crystal optics | |
| Refractive indices |
n α = 2.19 (calculated) n β = 2.25 n γ = 2.27 (calculated) |
| Birefringence | δ = 0.08 |
| Optical character | biaxial negative |
| Axis angle | 2V = 50 ° |
| Pleochroism | strong from X = Z = pale yellow to Y = brown |
Mounanaite is a very rare mineral from the mineral class of " phosphates , arsenates and vanadates ". It crystallizes in the monoclinic crystal system with the chemical composition PbFe 3+ 2 (VO 4 ) 2 (OH) 2 and is therefore chemically a lead - iron - vanadate with additional hydroxyl groups .
Mounanait developed after [001] {010} after stretched and platy crystals up to 0.3 mm size, which typically appear pseudohexagonal and together with Francevillit and Curienit in the oxidation zone of in sedimentary rocks seated uranium - Vanadium - deposits occur. Together with goethite , mounanaite also forms microcrystalline, crusty aggregates in crevices in the sandstone, which represent the matrix for vanuralite crystals. The type locality of the mineral is the "Mounana Mine" located 80 km northwest of Franceville in the province of Haut-Ogooué in Gabon .
Etymology and history
The material for the first description of the Mounanaite comes from two successive sampling campaigns in 1963 and 1964 in the "Mounana Mine", which was discovered in 1956 by the French geologists N. Morin and J. Lecomte from the French Commissariat à l'énergie atomique (CEA) was. During the determinations carried out a little later, a new mineral was recognized in this material. After intensive investigations by a French team of mineralogists and crystallographers led by Fabien Cesbron , the new mineral was presented to the International Mineralogical Association (IMA), which recognized it as a new mineral on December 31, 1968 with 15 votes in favor and no votes against. It was first described as Mounanaite by Fabien Cesbron and Jean Fritsche in 1969 in the French scientific magazine "Bulletin de la Societe française de Minéralogie et de Cristallographie". The authors named the mineral after its type locality, the UV deposit of the "Mounana Mine".
The uranium mining in the Gabonese deposits "Mounana" (1960-1999), "Oklo" (1970-19985), "Boyindzi" (1980-1991) and "Mikouloungou" (1997-1999) was via COMUF, a subsidiary of the French Energy company Compagnie Générale des Matières Nucléaires ( Cogéma , now AREVA ). The uranium mine "Mounana", which was closed in 1999 after 40 years of production, came from a large part of the fissile uranium required for French nuclear weapons and for French nuclear power plants. The uranium deposit of the “Oklo Mine”, which is not far from the “Mounana Mine”, became famous for the Oklo natural reactor , where a nuclear chain reaction started within a natural uranium concentration in the Precambrian , which came to a standstill 1.5 billion years ago at the latest.
The type material for Mounanait (Cotype) is stored under catalog number 11647 in the collection of the University of Pierre and Marie Curie (French Université Pierre et Marie Curie, UPMC, also Paris 6) in Paris and in the collection des Mines ParisTech (formerly: École nationale supérieure des mines de Paris ) in Paris ("Mission SCEM" 1962, catalog number unknown).
classification
The current classification of the International Mineralogical Association (IMA) counts the mounanaite to the tsumcorite group with the general formula Me (1) Me (2) 2 (XO 4 ) 2 (OH, H 2 O) 2 , in which Me (1), Me (2) and X different positions in the structure of the minerals of the tsumcorite group with Me (1) = Pb 2+ , Ca 2+ , Na + , K + and Bi 3+ ; Me (2) = Fe 3+ , Mn 3+ , Cu 2+ , Zn 2+ , Co 2+ , Ni 2+ , Mg 2+ and Al 3+ and X = As 5+ , P 5+ , V 5+ and represent S 6+ . To Tsumcoritgruppe include not only Mounanait still Cabalzarit , Cobaltlotharmeyerit , Cobalttsumcorit , Ferrilotharmeyerit , Gartrellit , Helmutwinklerit , Kaliochalcit , Krettnichit , Lotharmeyerit , Lukrahnit , Manganlotharmeyerit , Mawbyit , Natrochalcit , Nickellotharmeyerit , Nickelschneebergit , Nickeltsumcorit , Phosphogartrellit , Rappoldit , Schneebergit , Thometzekit , Tsumcorit , Yancowinnait and Zinc Gartrellite .
Already in the outdated 8th edition of the mineral classification according to Strunz , the mounanaite belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates, arsenates and vanadates with foreign anions " (large cations (and others)), where he in the appendix of the "Palermoit-Carminit-Gruppe" with the system no. VII / B.13 and its main members attakolite , bertossaite , carminite (here: carminite ) and palermoite .
In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , the mineral was given the system and mineral number. VII / C.31-70 . In the "lapis system" this also corresponds to the class of "phosphates, arsenates and vanadates", but in the section "water-containing phosphates, without foreign anions", where mounanaite together with cabalzarite, cobalt solder arerite, cobalt sumcorite, ferrilotharmerite, gartrellite, helmutwinklerite, Krettnichite, Lotharmeyerit, Lukrahnit, Manganlotharmeyerit, Mawbyit, Nickellotharmeyerit, Nickelschneebergit, Nickeltsumcorit, Phosphogartrellite, Rappoldit, Schneebergite, Thometzekit, Tsumcorite, Yancowinnait and Zinc Gartrellite form the "Gartrellit-Group" (Standcorit 2018).
The 9th edition of Strunz's mineral systematics , which has been valid since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also assigns the mounanaite to the category of “phosphates, etc. without additional anions; with H 2 O “. However, this is further subdivided according to the relative size of the cations involved and the molar ratio of phosphate, arsenate or vanadate complex to the water of crystallization content , so that the mineral is classified in the sub-section “With large and medium-sized cations; RO 4 : H 2 O = 1: 1 ”is to be found, where together with cabalzarite, cobalt solder armyerite, cobalt sumcorite, ferrilotharmeyerite, krettnichite, Lotharmeyerite, manganese solder armyerite, mawbyite, nickellotharmeyerite, nickel snow mountainite, snow mountainite, thomorite group“ Tsumcorite ”with Tsumcorite System no. 8.CG.15 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the mounanaite 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 Krettnichit in the " Mounanait group " with the system no. 41.10.07 within the subsection “Anhydrous phosphates etc., with hydroxyl or halogen with (A 2+ B 2+ ) 3 (XO 4 ) 2 Z q ”.
Chemism
Microprobe analyzes on Mounanait showed mean values of 38.47% PbO; <0.1% CaO; 26.01% Fe 2 O 3 ; 0.32% Al 2 O 3 ; <0.1% ZnO; 0.87% CuO; 29.28% V 2 O 5 ; 0.18% As 2 O 5 ; 0.81% P 2 O 5 ; <0.11% SO 3 and 3.21% H 2 O (calculated content). The empirical formula Pb 1.02 (Fe 1.92 Al 0.04 Cu 0.06 ) Σ = 2.02 [(VO 4 ) 1.92 (PO 4 ) 0, is calculated from them on the basis of 10 oxygen atoms , 04 (AsO 4 ) 0.01 ] Σ = 2.00 (OH) 2.04 , which has been simplified to PbFe 3+ 2 (VO 4 ) 2 (OH) 2 . The latter requires 38.30% PbO, 27.40% Fe 2 O 3 , 31.21% V 2 O 5 and 3.09% H 2 O.
Mounanait is a representative of the tsumcorite group . The general formula for the tsumcorite group is Me (1) Me (2) 2 ( X O 4 ) 2 O (1) with Me (1) = Pb, Ca, Na, K and Bi; Me (2) = Fe, Mn, Cu, Zn, Co, Ni and Al; X = P, As, V and S as well as O (1) = H 2 O, OH and F. Mixed crystal formation takes place mainly on the Me (2) position, but less frequently on the X and Me (1) position .
Since there are only trivalent cations in the Mounanait on the Me (2) position, the O (1) position is exclusively occupied by hydroxyl groups , a substitution by water molecules (H 2 O) is therefore not necessary. A partial replacement of hydroxyl groups by fluoride ions (F - ) is considered very likely.
Mounanaite is the Fe 3+ -dominant analogue of the Mn 3+ -dominated krettnichite. A zinc-free mawbyite would form the arsenate-dominant analogue of the vanadate-dominated mounanaite.
Crystal structure
Mounanaite crystallizes in the monoclinic crystal system in the space group C 2 / m (space group no. 12) with the lattice parameters a = 9.294 Å ; b = 6.166 Å; c = 7.713 Å and β = 115.57 ° as well as two formula units per unit cell . In the first description, Mounanait was described as triclinic.
The crystal structure of the mounanaite consists of Fe 3+ O 6 coordination octahedra , which are linked by common edges to form chains parallel [010]. VO 4 - Tetrahedra with common corners connect these chains, creating layers parallel to the ab-surface. The layers are connected by hydrogen bonds and by Pb [6 + 2] atoms which occupy specific positions with symmetry 1 between these layers. Fe at the Me (2) position is coordinated in an octahedral manner (compare the adjacent figures for the crystal structure).
Mounanaite is isotypic (isostructural) to those monoclinic minerals of the tsumcorite group that crystallize in the space group C 2 / m (space group no. 12) . These include not only Cabalzarit, Cobaltlotharmeyerit, Cobalttsumcorit, Ferrilotharmeyerit, Krettnichit, Lotharmeyerit, Manganlotharmeyerit, Mawbyit, Nickellotharmeyerit, Nickelschneebergit, Nickeltsumcorit, Schneebergit, Thometzekit and Tsumcorit also Natrochalcit and Kaliochalcit .
properties
morphology
According to [001], Mounanait develops elongated and according to {010} platy, very large-area crystals up to 0.3 mm in size, which typically appear pseudo-hexagonal due to the pinacoid {010} which determines the region and the more or less balanced remaining surface forms. The pinacoids {100}, {110}, {01 1 }, {02 1 }, {11 1 }, {12 1 }, { 1 2 1}, {0 2 1} were found on further crystal forms - with a triclinic arrangement and identified the very rare pinacoid {011} (compare the crystal drawing opposite). Mounanaite often forms crystals according to two different laws. These include rotation twins around [001] and twins with - in the case of a triclinic arrangement - (1 1 1) or - in the case of a monoclinic arrangement - (1 1 0) as a twin level. Mounanaite also occurs in crevices in the sandstone together with goethite in the form of microcrystalline aggregates.
physical and chemical properties
The crystals of the mounanaite are reddish brown, its line color is not specified, but should be a light brown. According to the high values for light refraction (n x = 2.19, n z = 2.27), the surfaces of the translucent to transparent crystals have a diamond-like sheen .
The mineral shows good cleavability according to (001). With a Mohs hardness of 4.5, mounanaite is one of the medium-hard minerals, so it stands between the reference minerals fluorite (hardness 4) and apatite (hardness 5) and can be easily scratched with a pocket knife like these more (fluorite) or less (apatite). The measured density of the mineral is 4.85 g / cm³, its calculated density is 4.88–4.89 g / cm³.
Education and Locations
Mounanaite is a typical secondary mineral which is formed by weathering of primary ore minerals in the oxidation zone of hydrothermal uranium-vanadium deposits . It originated from the decomposition of uranium and vanadium-containing ore minerals, such as uraninite and Coffinit and Karelianit , montroseite and roscoelite , wherein the vanadium from the decomposition of the vanadium and iron minerals from the weathering of primary iron sulfides such as marcasite , pyrite and greigite originates.
The tiny mounanaite crystals and aggregates form the matrix or the substrate for various secondary uranium minerals. The Ba-Pb-uranyl vanadate Francevillit and curienite sit on red-brown mounanaite crystals, crystals of the Al-uranyl vanadate vanuralite formed on crust-like mixtures with goethite.
As a very rare mineral formation, Mounanaite could so far (as of 2017) only be described by its type locality and one other site. The type locality is the "Mounana Mine" near northwest of Franceville in the province of Haut-Ogooué in Gabon . Another discovery site for mounanaite are uranium prospects in Val Rendena near Bocenago and Spiazzo , Valli Giudicarie , Trentino ( Italian Provincia autonoma di Trento ) in the southern part of the Trentino-Alto Adige region , Italy . Locations for Mounanait in Austria and Switzerland are therefore unknown.
use
Due to its rarity, mounanaite is only of interest to the mineral collector.
See also
literature
- Fabien Cesbron, Jean Fritsche: La mounanaïte, nouveau vanadate de fer et de plomb hydraté . In: Bulletin de la Societe française de Minéralogie et de Cristallographie . tape 92 , 1969, p. 196–202 (French, rruff.info [PDF; 495 kB ; accessed on May 26, 2020]).
- Mounanaite . 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; 67 kB ; accessed on May 26, 2020]).
- Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 634 (first edition: 1891).
Web links
- Mineral Atlas: Mounanaite (Wiki)
- Mounanaite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 26, 2020 .
- David Barthelmy: Mounanaite Mineral Data. In: webmineral.com. Retrieved May 26, 2020 (English).
- American-Mineralogist-Crystal-Structure-Database - Mounanaite. In: rruff.geo.arizona.edu. Retrieved May 26, 2020 (English).
Individual evidence
- ↑ a b c d e f g h i j k l m n o p q r s t Werner Krause, Klaus Belendorff, Heinz-Jürgen Bernhardt, Catherine McCammon, Herta Effenberger, Werner Mikenda: Crystal chemistry of the tsumcorite-group minerals. New data on ferrilotharmeyerite, tsumcorite, thometzekite, mounanaite, helmutwinklerite, and a redefinition of gartrellite . In: European Journal of Mineralogy . tape 10 , 1998, pp. 179-206 , doi : 10.1127 / ejm / 10/2/0179 .
- ↑ a b c d e f g h i j k l m n o Fabien Cesbron, Jean Fritsche: La mounanaïte, nouveau vanadate de fer et de plomb hydraté . In: Bulletin de la Societe française de Minéralogie et de Cristallographie . tape 92 , 1969, p. 196–202 (French, rruff.info [PDF; 495 kB ; accessed on May 26, 2020]).
- ^ 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. 485 .
- ^ Mounanaite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 26, 2020 .
- ^ A b c d Fabien Cesbron, Pierre Bariand: The Uranium-Vanadium Deposit of Mounana, Gabon . In: The Mineralogical Record . tape 6 , no. 5 , 1975, p. 237-249 .
- ↑ Mounana, Gabon. Uranium mining. In: www.nuclear-risks.org. Retrieved May 26, 2020 .
- ↑ a b Mounanaite . 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; 67 kB ; accessed on May 26, 2020]).
- ↑ Catalog of Type Mineral Specimens - M. (PDF 124 kB) In: docs.wixstatic.com. Commission on Museums (IMA), December 12, 2018, accessed May 26, 2020 .
- ↑ 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 .
- ↑ Ernest H. Nickel , Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF; 1.82 MB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed May 27, 2020 .
- ↑ Joël Brugger, Thomas Armbruster, Alan Criddle, Peter Berlepsch, Stefan Graeser, Shane Reeves: Description, crystal structure, and paragenesis of krettnichite, PbMn 3+ 2 (VO 4 ) 2 (OH) 2 , the Mn 3+ analogue of mounanaite . In: European Journal of Mineralogy . tape 13 , 2001, p. 145–158 , doi : 10.1127 / 0935-1221 / 01 / 0013-0145 (English, pdfs.semanticscholar.org [accessed on May 26, 2020]).
- ↑ Localities for Mounanaite. In: mindat.org. Hudson Institute of Mineralogy, accessed May 26, 2020 .
- ↑ List of locations for mounanaite in the Mineralienatlas and Mindat , accessed on May 26, 2020.
- ↑ Italo Campostrini: Minerali secondari dei giacimenti uraniferi nelle Arenarie di Val Gardena del Trentino Occidentale (Alpi Meridionali, Italia) . In: Studi trentini di scienze naturali . tape 93 , 2013, p. 89-114 (Italian).