Torbernite

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Torbernite
Torbernite-120981.jpg
Torbernite crystals from Mashamba West Mine, Kolwezi, Katanga Province, Democratic Republic of the Congo
General
Category Phosphate minerals
Formula
(repeating unit)		Cu[(UO2)(PO4)]2(H2O)12 [1]
IMA symbol Tor [2]
Strunz classification 8.EB.05
Crystal system Tetragonal
Crystal class Ditetragonal dipyramidal (4/mmm)
H-M symbol: (4/m 2/m 2/m) [3]
Space group I4/mmm [4]
Identification
Formula mass 641 – 713 g/mol, depending the degree of water loss
ColorEmerald green to apple green [5]
Crystal habit Tabular crystals; Foliated to earthy masses and encrustations
Twinning Rare on [110]
Cleavage [001] Perfect; [100] Distinct [5]
Fracture Brittle [5]
Mohs scale hardness2–2.5 [5]
Luster Vitreous; pearly [5]
Streak Pale green
Diaphaneity Transparent to subtranslucent
Density measured: 3.22; calculated: 3.264(1) [5]
Optical propertiesUniaxial (−)
Refractive index nω = 1.590 – 1.592 nε = 1.581 – 1.582 [3]
Birefringence δ = 0.009 – 0.010 [3]
Pleochroism Visible
Melting point Decomposes before
Fusibility Decomposes before
Other characteristics Radioactive.svg Radioactive and Poisonous Hazard T.svg

Torbernite, also known as chalcolite, [6] is a relatively common mineral with the chemical formula Cu[(UO2)(PO4)]2(H2O)12. [1] It is a radioactive, hydrated green copper uranyl phosphate, found in granites and other uranium-bearing deposits as a secondary mineral. The chemical formula of torbernite is similar to that of autunite in which a Cu2+ cation replaces a Ca2+ cation. Torbernite tends to dehydrate to metatorbernite with the sum formula Cu[(UO2)(PO4)]2(H2O)8.

Contents

Etymology and history

Torbern Olof Bergman Torbern Olof Bergman.jpg
Torbern Olof Bergman

Torbernite was found for the first time at Georg Wagsfort Mine near Johanngeorgenstadt in the Erzgebirge Mountains in Saxony. It was first mentioned in 1772 by Ignaz von Born in his work Lythophylacium Bornianum, calling it "mica viridis crystallina, ibid." (green crystalline mica from Johanngeorgenstadt, Sax.; ibid. = "as the item above"). In 1780 Abraham Gottlob Werner uses Born's work and describes the mineral in more detail, calling it at first "grüner Glimmer" (green mica), later naming it "torbernite" in honour of the Swedish mineralogist and chemist Torbern Olof Bergman (1735–1784). [7]

Classification

According to the International Mineralogical Association (IMA), which last updated its list in 2009, [8] the Nickel-Strunz system lists torbernite in the section of "uranyl phosphates and arsenates". There it is part of the sub-section "UO2 : RO4 = 1 : 1", forming the autunite group along with autunite, heinrichite, kahlerite, kirchheimerite, metarauchite, nováčekite-I, nováčekite-II, saléeite, uranocircite I, uranocircite II, uranospinite, xiangjiangite and zeunerite with system number 8.EB.05.

Dana groups the mineral into the class "phosphates, arsenates and vanadates", into the section "hydrated phosphates etc." into an unnamed group with metatorbernite, number 40.02a.13.

Crystal structure

Packing of torbernite. Colour code: uranium, copper, phosphorus, oxygen, water, hydrogen Torbernite - packing.png
Packing of torbernite. Colour code: uranium , copper , phosphorus , oxygen , water , hydrogen

Torbernite crystallises in the tetragonal space group I4/mmm with the lattice parameters a = 7.0267(4) Å und c = 20.807(2) Å and 2 formula units per unit cell. [1]

In a study in 2003, using fresh, synthetic crystals, Locock and Burns have compared the crystal structures of the copper uranyl phosphates torbernite, Cu[(UO2)(PO4)]2(H2O)12 and metatorbernite, Cu[(UO2)(PO4)]2(H2O)8 with those of the copper uranyl arsenates zeunerite, Cu[(UO2)(AsO4)]2(H2O)12, and metazeunerite, Cu[(UO2)(AsO4)]2(H2O)8. In these studies they were able to finally analyse the crystal structure of torbernite for the very first time, and to get a significantly more precise analysis for the structure of metatorbernite, compared with previous studies (Makarov and Tobelko R1 = 25 %, [9] Ross et al. R1 = 9.7 %, [10] Stergiou et al. R1 = 5.6 %, [11] Calos and Kennard R1 = 9.2 % [12] vs. Locock und Burns R1 = 2.3 %).

The study shows that torbernite is isostructural to zeunerite, and metatorbernite is isostructural to metazeunerite. All four compounds are of the layered autunite type with the [(UO2)(XO4)]- structural motif (with X = P or As). The Cu2+ ions are coordinated in a square-planar fashion by water molecules in all these compounds, and further coordinate to the uranyl oxygen atoms, forming octahedra with Jahn-Teller distortion. The additional water molecules are held in the crystal structure only by hydrogen bridges.

Metatorbernite

Metatorbernite from Margabal Mine, Entraygues-sur-Truyere, France (Size: 4 cm x 3 cm x 1.8 cm) Metatorbernite sapin.jpg
Metatorbernite from Margabal Mine, Entraygues-sur-Truyère, France (Size: 4 cm × 3 cm × 1.8 cm)

Torbernite dehydrates readily to metatorbernite with the sum formula Cu[(UO2)(PO4)]2(H2O)8. It forms as torbernite withers, and can also be obtained by artificially heating torbernite above 75 °C. [13] The crystals are rather opaque and only weakly translucent with a glassy lustre. [14]

Metatorbernite crystallises tetragonally-dipyramidally in space group P4/n with the lattice parameters a = 6.9756(5) Å and c = 17.349(2) Å and 2 formula units per unit cell. [1]

Packing of metatorbernite. Colour code: uranium, copper, phosphorus, oxygen, water, hydrogen Metatorbernite - Locock, Burns - packing.png
Packing of metatorbernite. Colour code: uranium, copper, phosphorus, oxygen, water, hydrogen

The crystal structure of metatorbernite is different from torbernite as every second uranyl phosphate layer is moved about one half of the length of the crystallographic a-axis in the directions [100] and [010]. [1] The analysis by Locock and Burns confirms the finding by Stergiou et al., that the Cu2+ ions only have an 88% crystallographic occupancy. The authors assume that by protonation of some of the water molecules there is a charge compensation for electronic neutrality, as it is discussed with the mineral chernikovite. [1] The same is postulated by the same authors for autunite. [15] Due to the limitations of X-ray diffraction this postulate is practically not verifiable with this method.

The analysis by Locock and Burns shows eight molecules of water per formula unit in metatorbernite. This is in accord with the works by Arthur Francis Hallimons [13] [16] and Kurt Walenta, [17] who show that the different steps of hydration between torbernite and metatorbernite have clear boundaries, and the water content of each compound remains constant and does not vary, in contrast for instance, as seen in minerals of the zeolite group. Therefore, sum formulae indicating varying degrees of water for torbernite and metatorbernite must not be used. [1]

Properties

A pyramidal torbernite crystal from Brest, France (Field of view: 7 mm x 5 mm) Torbernite - Kerguillo quarry, Bohars, Brest, Finistere, Brittany, France.jpg
A pyramidal torbernite crystal from Brest, France
(Field of view: 7 mm × 5 mm)
Intergrowth of dipyramidal crystals of metatorbernite in a geode from Les Montmins Mine (Ste Barbe Ader), Echassieres, Kanton Ebreuil, Departement Allier, Auvergne, France (Field of view: 1 mm x 1 mm) Metatorbernite - Les Montmins Mine, Echassieres, Ebreuil, Allier, Auvergne, France.jpg
Intergrowth of dipyramidal crystals of metatorbernite in a geode from Les Montmins Mine (Ste Barbe Ader), Échassières, Kanton Ébreuil, Département Allier, Auvergne, France (Field of view: 1 mm × 1 mm)

Morphology

The mineral is often encountered as small thin tabular crystals, but may also be flaky or powdery. More rare are thicker plates, resembling a stacked deck of cards. More frequent than these are dipyramidal forms.

Physical and chemical properties

Because of its uranium content of about 48 % the material is strongly radioactive. According to the sum formula a specific activity of 85.9 kBq/g [3] can be given (for comparison: natural potassium: 0.0312 kBq/g).

Contrary to its calcium analogue autunite the mineral does not fluoresce. [6] The mineral is very brittle. Its hardness (Mohs) is between 2 and 2.5.

Occurrence and localities

Paragenisis of kasolite (yellow, acicular) with torbernite (green, platy) Wulfenite-Kasolite-Torbernite-214957.jpg
Paragenisis of kasolite (yellow, acicular) with torbernite (green, platy)

Torbernite forms as a secondary mineral on the oxidation zone of uranium ores. It is often found in paragenesis with autunite, metatorbernite, uraninite, zeunerite and, very rarely, with gauthierite. [18]

Torbernite is relatively common, and world-wide there are more than 1100 documented localities known by 2022. [19] In Germany it is known not only from its type locality Johanngeorgenstadt, but also from other areas in the Ore Mountains, as well as from the Black Forest, Fichtel Mountains, Bavarian Forest, Thuringian Forest. Further localities are in Argentina, Australia, Austria, Belgium, Bolivia, Brazil, Canada, Chile, China, Czech Republic, Democratic Republic of the Congo, France, Gabon, Ireland, Italy, Japan, Madagascar, Mexico, Namibia, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, South Africa, Switzerland, Tajikistan, Uzbekistan, the United Kingdom and the United States. [20]

Precautions

A torbernite specimen from the Margabal Mine in the Midi-Pyrenees, France Torbernite-237463.jpg
A torbernite specimen from the Margabal Mine in the Midi-Pyrénées, France

Because of the inherent toxicity of uranium compounds, samples of this mineral should be kept in air tight glass jars.

See also

Related Research Articles

<span class="mw-page-title-main">Autunite</span> Type of phosphate mineral

Autunite (hydrated calcium uranyl phosphate), with formula Ca(UO2)2(PO4)2·10–12H2O, is a yellow-greenish fluorescent phosphate mineral with a hardness of 2–2+1⁄2. Autunite crystallizes in the orthorhombic system and often occurs as tabular square crystals, commonly in small crusts or in fan-like masses. Due to the moderate uranium content of 48.27% it is radioactive and also used as uranium ore. Autunite fluoresces bright green to lime green under UV light. The mineral is also called calco-uranite, but this name is rarely used and effectively outdated.

<span class="mw-page-title-main">Phosphate mineral</span> Nickel–Strunz 9 ed mineral class number 8 (isolated tetrahedral units, mainly)

Phosphate minerals are minerals that contain the tetrahedrally coordinated phosphate anion, sometimes with arsenate and vanadate substitutions, along with chloride (Cl−), fluoride (F−), and hydroxide (OH−) anions, that also fit into the crystal structure.

<span class="mw-page-title-main">Abernathyite</span>

Abernathyite is a mineral with formula K(UO2)(AsO4)·3H2O. The mineral is named after Jesse Evrett Abernathy (1913–1963) who first noted it in 1953 in the U.S. State of Utah. It was described as a new mineral species in 1956. Abernathyite is yellow and occurs as small crystals.

The uranyl ion is an oxycation of uranium in the oxidation state +6, with the chemical formula UO2+
2. It has a linear structure with short U–O bonds, indicative of the presence of multiple bonds between uranium and oxygen. Four or more ligands may be bound to the uranyl ion in an equatorial plane around the uranium atom. The uranyl ion forms many complexes, particularly with ligands that have oxygen donor atoms. Complexes of the uranyl ion are important in the extraction of uranium from its ores and in nuclear fuel reprocessing.

<span class="mw-page-title-main">Metatorbernite</span>

Metatorbernite is a radioactive phosphate mineral, and is a dehydration pseudomorph of torbernite. Chemically, it is a copper uranyl phosphate and usually occurs in the form of green platy deposits. It can form by direct deposition from a supersaturated solution, which produces true crystalline metatorbernite, with a dark green colour, translucent diaphaneity, and vitreous lustre. However, more commonly, it is formed by the dehydration of torbernite, which causes internal stress and breakage within the crystal lattice, resulting in crystals composed of microscopic powder held together using electrostatic force, and having a lighter green colour, opaque diaphaneity, and a relatively dull lustre. As with torbernite, it is named after the Swedish chemist Torbern Bergman. It is especially closely associated with torbernite, but is also found amongside autunite, meta-autunite and uraninite.

<span class="mw-page-title-main">Arthurite</span> Arsenate mineral

Arthurite is a mineral composed of divalent copper and iron ions in combination with trivalent arsenate, phosphate and sulfate ions with hydrogen and oxygen. Initially discovered by Sir Arthur Russell in 1954 at Hingston Down Consols mine in Calstock, Cornwall, England, arthurite is formed as a resultant mineral in the oxidation region of some copper deposits by the variation of enargite or arsenopyrite. The chemical formula of Arthurite is CuFe23+(AsO4,PO4,SO4)2(O,OH)2·4H2O.

<span class="mw-page-title-main">Althupite</span> Aluminium thorium uranyl phosphate mineral

Althupite (IMA symbol: Ahp) is a rare aluminium thorium uranyl phosphate mineral with complex formula written as AlTh(UO2)7(PO4)4O2(OH)5·15H2O, from a granitic pegmatite. It is named after its composition (ALuminium, THorium, Uranium, and Phosphorus).

<span class="mw-page-title-main">Bergenite</span>

Bergenite is a rare uranyl phosphate of the more specific phosphuranylite group. The phosphuranylite-type sheet in bergenite is a new isomer of the group, with the uranyl phosphate tetrahedra varying in an up-up-down, same-same-opposite (uuduudSSOSSO) orientation. All bergenite samples have been found in old mine dump sites. Uranyl minerals are a large constituent of uranium deposits.

<span class="mw-page-title-main">Cyrilovite</span>

Cyrilovite (NaFe33+(PO4)2(OH)4·2(H2O)) is a hydrous sodium iron phosphate mineral. It is isomorphous and isostructural with wardite, the sodium aluminium counterpart.

<span class="mw-page-title-main">Boltwoodite</span> Hydrated potassium uranyl silicate mineral

Boltwoodite is a hydrated uranyl silicate mineral with formula (K0.56Na0.42)[(UO2)(SiO3OH)]·1.5(H2O), distinct in crystal structure from sodium boltwoodite, which has an orthorhombic structure rather than monoclinic. It is formed from the oxidation and alteration of primary uranium ores. It takes the form of a crust on some sandstones that bear uranium. These crusts tend to be yellowish with a silky or vitreous luster.

<span class="mw-page-title-main">Tsumebite</span>

Tsumebite is a rare phosphate mineral named in 1912 after the locality where it was first found, the Tsumeb mine in Namibia, well known to mineral collectors for the wide range of minerals found there. Tsumebite is a compound phosphate and sulfate of lead and copper, with hydroxyl, formula Pb2Cu(PO4)(SO4)(OH). There is a similar mineral called arsentsumebite, where the phosphate group PO4 is replaced by the arsenate group AsO4, giving the formula Pb2Cu(AsO4)(SO4)(OH). Both minerals are members of the brackebuschite group.

<span class="mw-page-title-main">Curite</span>

Curite is a rare mineral with the chemical composition Pb3[(UO2)4|O4|(OH)3]2·2 H2O. It is therefore a hydrated lead uranyl oxide, which forms red needles or orange, massive aggregates.

Paulscherrerite, UO2(OH)2, is a newly named mineral of the schoepite subgroup of hexavalent uranium hydrate/hydroxides. It is monoclinic, but no space group has been determined because no single-crystal study has been done. Paulscherrerite occurs as a canary yellow microcrystalline powdery product with a length of ~500 nm. It forms by the weathering and ultimate pseudomorphism of uranium-lead bearing minerals such as metaschoepite. The type locality for paulscherrerite is the Number 2 Workings, Radium Ridge near Mount Painter, North Flinders Ranges, South Australia, an area where radiogenic heat has driven hydrothermal activity for millions of years. It is named for Swiss physicist Paul Scherrer, co-inventor of the Debye-Scherrer X-ray powder diffraction camera. Study of paulscherrerite and related minerals is important for understanding the mobility of uranium around mining sites, as well as designing successful strategies for the storage of nuclear weapons and the containment of nuclear waste.

Bijvoetite-(Y) is a very rare rare-earth and uranium mineral with the formula (Y,REE)8(UO2)16(CO3)16O8(OH)8·39H2O. When compared to the original description, the formula of bijvoetite-(Y) was changed in the course of crystal structure redefinition. Bijvoetite-(Y) is an example of natural salts containing both uranium and yttrium, the other examples being kamotoite-(Y) and sejkoraite-(Y). Bijvoetite-(Y) comes from Shinkolobwe deposit in Republic of Congo, which is famous for rare uranium minerals. The other interesting rare-earth-bearing uranium mineral, associated with bijvoetite-(Y), is lepersonnite-(Gd).

Metarauchite is a member of the autunite group, found at the Jáchymov ore district, Czech Republic and in Schneeberg, Germany. The autunite group is a group of structured uranyl phosphates and arsenates; the other members of the group are autunite, bassetite, heinrichite, kahlerite, nováčekite-I, nováčekite-II, rauchite, sabugalite, saléeite, torbernite, uranocircite, uranospinite, and zeunerite. The mineral is named after Czech mineral collector Luděk Rauch, who died in the Jáchymov mines during mineral prospecting.

<span class="mw-page-title-main">Serrabrancaite</span>

Serrabrancaite is a mineral with the chemical formula MnPO4•H2O and which is named for the locality where it was found, the Alto Serra Branca Pegmatite. The Alto Serra Branca mine has been in operation since the 1940s. It is located in Paraiba, Brazil near a village named Pedra Lavrada. Tantalite is the main mineral mined here. Specimens of serrabrancaite are kept in the Mineralogical Collections of both the Bergakademie Freiberg, Germany and the Martin-Luther Universität Halle, Institut für Geologische Wissenschaften.

The phosphate sulfates are mixed anion compounds containing both phosphate and sulfate ions. Related compounds include the arsenate sulfates, phosphate selenates, and arsenate selenates.

<span class="mw-page-title-main">Gauthierite</span> Hydrous oxyuranyl mineral

Gauthierite is a very rare mineral with the idealised chemical sum formula KPb[(UO2)7O5(OH)7]·8H2O. It is a radioactive, hydrated orange-coloured lead potassium uranyl oxide hydroxide. It was found by analysing old mineral specimens, and is only known from one locality, the Shinkolobwe Mine in the Democratic Republic of the Congo. The mineral was named in honour of Gilbert Gauthier, a Belgian collector of uranium minerals, who provided a sample to one of the co-authors of the study that first identified it in 2017.

Uramphite is a rarely-found phosphate mineral in the "phosphate, arsenate and vanadate" mineral class with chemical composition (NH4)2[UO2PO4]2·6H2O from which it is seen to be a hydrated ammonium uranyl phosphate.

References

  1. 1 2 3 4 5 6 7 A. J. Locock, P. C. Burns: Crystal structures and synthesis of the copper-dominant members of the autunite and meta-autunite groups: torbernite, zeunerite, metatorbernite and metazeunerite In: The Canadian Mineralogist 2003, 41, 489–502 (PDF 2500 kB)
  2. ↑ L. N. Warr: IMA–CNMNC approved mineral symbols In: Mineralogical Magazine 2021, 85 291–320 (PDF 320 kB)
  3. 1 2 3 4 David Barthelmy (2022-10-10). "Torbernite Mineral Data". webmineral.com.
  4. ↑ K. H. Strunz, E. H. Nickel: Strunz Mineralogical Tables. Chemical-structural Mineral Classification System 2001, 9, E. Schweizerbart’sche Verlagsbuchhandlung (Nägele u. Obermiller), Stuttgart, 524 pages. ISBN   3-510-65188-X
  5. 1 2 3 4 5 6 J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols (Eds.): Torbernite In: Handbook of Mineralogy, Mineralogical Society of America 2001 (PDF 63 kB)
  6. 1 2 F. Klockmann: Klockmanns Lehrbuch der Mineralogie 1978, 16, Enke, Stuttgart, 655 pages. ISBN   3-432-82986-8
  7. ↑ T. Witzke. "Entdeckung von Torbernit". www.strahlen.org/tw.
  8. ↑ E. H. Nickel, M. C. Nichols: IMA/CNMNC List of Minerals 2009 ( http://cnmnc.main.jp/IMA2009-01%20UPyear%20160309.pdf PDF 1.82 MB])
  9. ↑ E. S. Makarov, K. I. Tobelko: Crystal structure of metatorbernite In: Doklady Akademii Nauk SSSR 1960, 131, 87–89
  10. ↑ M. Ross, H. T. Evans Jr., D. E. Appleman: Studies of the torbernite minerals. II. The crystal structure of metatorbernite In: American Mineralogist 1964, 49, 1603–1621 (PDF 1126 kB)
  11. ↑ A. C. Stergiou, P. J. Rentzeperis, S. Sklavounos: Refinement of the crystal structure of metatorbernite In: Zeitschrift für Kristallographie 1993, 205 1–7 (PDF 391 kB)
  12. ↑ N. J. Calos, C. H. L. Kennard: Crystal structure of copper bis(uranyl phosphate) octahydrate (metatorbernite), Cu(UO2PO4)2·8(H2O) In: Zeitschrift für Kristallographie 1996, 211, 701–702 (PDF 85.1 kB)
  13. 1 2 A. F. Hallimond: The crystallography and dehydration of torbernite In: Mineralogical Magazine 1916, 17 (82), 326–339 (PDF 559 kB)
  14. ↑ "Metatorbernite". mindat.org. Hudson Institute of Mineralogy. 2022-10-10.
  15. ↑ A. J. Locock, P. C. Burns: The crystal structure of synthetic autunite, Ca[(UO2)(PO4)]2(H2O)11 In: American Mineralogist 2003, 88, 240–244 (PDF 408 kB)
  16. ↑ A. F. Hallimond: Meta-torbernite I. Its physical properties and relation to torbernite In: Mineralogical Magazine 1920, 19 (89), 43–47 (PDF 228 kB)
  17. ↑ K. Walenta: Beiträge zur Kenntnis seltener Arsenatmineralien unter besonderer Berücksichtigung von Vorkommen des Schwarzwaldes In: Tschermaks mineralogische und petrographische Mitteilungen (Mineralogy & Petrology) 1964, 9 (3), 252–282 (online)
  18. ↑ T. A. Olds, J. Plášil, A. R. Kampf, R. Škoda, P. C. Burns, J. Čejka, V. Bourgoin and J.-C. Boulliard: Gauthierite, KPb[(UO2)7O5(OH)7]·8H2O, a new uranyl-oxide hydroxy-hydrate mineral from Shinkolobwe with a novel uranyl-anion sheet-topology In: European Journal of Mineralogy 2017, 20, 129–141 (Weblink)
  19. ↑ "Localities for Torbernite". mindat.org. Hudson Institute of Mineralogy. 2022-10-10.
  20. ↑ List of localities for torbernite at Mineralienatlas (German) and at Mindat (English).
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