|General and classification|
(and division, if applicable)
|Sulphides and sulphosalts|
|System No. according to Strunz
and according to Dana
|Crystal class; Symbol||cubic hexakisoctahedral; 4/m 3 2/m|
|Room group||Fd3m(No. 227)|
|Lattice parameters||a= 9.92 Å|
|Form units||Z = 8|
|Mohs hardness||5 to 5.5 (VHN30 = 578 kg/mm2)|
|Density (g/cm3)||calculated: 7.24|
|Fracture; Tenacity||very brittle|
|Color||iron black, grey in incident light|
Cuproiridsite is a rarely occurring mineral in the mineral class “sulfides and sulfosalts” with the chemical composition CuIr2S4 and thus chemically seen a copper-iridium sulfide. Structurally cuproiridsite belongs to the group of spinels.
Cuproiridsite crystallizes in the cubic crystal system, but has so far only been found in the form of tiny inclusions up to about 300 μm in isoferroplatinum and platinum. The mineral is completely opaque and of iron-black, in reflected light also gray, color with a metallic luster on the surfaces.
Etymology and history
Cuproiridsite was first discovered together with cuprorhodsite in mineral samples from Mount Filipp (Russian гора Филиппа) on the Kamchatka Peninsula, as well as from the Kondjor Massif and the nearby Chad Mass if in the Aldan Highlands on the territory of the Sakha Republic (Yakutia) in the Khabarovsk Region of the Russian Far East Federal District. All three sites are therefore considered to be the type locality for cuproiridsite. The analysis and initial description were made by N. S. Rudashevsky, Y. P. Menshikov, A. G. Mochalov, N. V. Trubkin, N. I. Shumskaya, V. V. Zhdanov (Russian: Н. С. Рудашевский, Ю. П. Меньшиков, А. Г. Мочалов, Н. В. Трубкин, Н. И. Шумская, В. В. Жданов), who named the mineral after its chemical composition of copper (Latin cuprum, as part of the name cupro-) and iridium.
Rudashevsky’s team of mineralogists submitted their test results and the chosen name for consideration to the International Mineralogical Association in 1984 (IMA internal accession no.: 1984-016), which recognized cuproiridsite as a distinct mineral species. The publication followed a year later in the Russian journal Записки Всесоюзного Минералогического Общества [Sapiski Vsessojusnogo Mineralogitscheskogo Obschtschestwa] and was confirmed again in 1986 with the publication of the New Mineral Names in the English-language journal American Mineralogist.
The type material of the mineral is kept in the Mineralogical Collection of the Saint Petersburg State Mining University (formerly the State Mining Institute) in Saint Petersburg under Collection No. 1686/1.
The IMA structural classification places cuproiridsite in the spinel supergroup, where it forms the “carrollite subgroup” within the “thiospinels” along with carrollite, cuprocalinite, fletcherite, florensovite, malanite, rhodostannite, and toyohaite (as of 2019).
The known mineral systematics, which initially classify cuproiridsite according to chemical composition, place it in the mineral class of “sulfides and sulfosalts”.
Since the cuproiridsite was recognized only in 1984 as an independent mineral, it is not yet listed in the since 1977 outdated 8th edition of the mineral systematics according to Strunz. Only in the Lapis mineral directory according to Stefan Weiß, which out of consideration for private collectors and institutional collections still follows this old form of the systematics of Karl Hugo Strunz, the mineral received the system and mineral no. II/D.02-30. In the “Lapis systematics” this corresponds to the section “sulfides with [the molar ratio] metal : S,Se,Te < 1 :1”, where cuproiridsite together with cuprorhodsite, ferrorhodsite (discredited as identical to cuprorhodsite; IMA 2017-H), kingstonite, malanite and xingzhongite form a distinct but unnamed group/the “Group” (as of 2018).
The since 2001 valid and updated by the IMA until 2009 9. Edition of Strunz’s mineral systematics classifies cuproiridsite in the division “metal sulfides with M : S = 3 : 4 and 2 : 3”. This is also further subdivided according to the exact molar ratio, so that the mineral can be found according to its composition in the subdivision “M : S = 3 :4”, where it is to be found together with bornhardtite, cadmoindite, carrollite, cuprorhodsite, daubréelite, ferrorhodsite, fletcherite, florensovite, greigite, indite, kalininite, linneite, malanite, polydymite, siegenite, trüstedtite, tyrrellite, violarite and xingzhongite the “linneite group” system no. 2.DA.05 forms.
The system of minerals according to Dana, which is predominantly used in English-speaking countries, also classifies cuproiridsite in the class of “sulphides and sulphosalts” and there in the division of “sulphide minerals”. Here it is to be found in the “Linneitgruppe (Isometrisch: Fd3mVorlage)” with the system no. 02.10.01 within the subdivision “sulfides – including selenides and tellurides – with the compositionAmBnXp, with (m+n) : p = 3 : 4″.
In the (theoretically) ideal, i.e., pure composition of cuproiridsite (CuIr2S4), the mineral consists of copper (Cu), iridium (Ir), and sulfur (S) in a molar ratio of 1 : 2 : 4, which corresponds to a mass fraction (wt.%) of 11.03 wt% by weight Cu, 66.71 % by weight Ir and 22.26 % by weight S.
In contrast, a total of 26 microprobe analyses on the type material from Kamchatka yielded the deviating average composition of 7.41 wt.% Cu, 48.9 wt.% Ir and 24.6 wt.% S. In addition, proportions of 3.17 wt.% iron (Fe) and 0.27 wt.% nickel (Ni) as well as 10.5 wt.% platinum (Pt) and 6.05 wt.% rhodium (Rh) were measured, representing part of the copper and part of the iridium, respectively, in the formula diadoch.
On the basis of four sulfur atoms, the empirical formula (Cu0.61Fe0.30Ni0.02)Σ=0.93(Ir1.38Pt0.28Rh0.31)Σ=1.92S4.00 is calculated from the measured values, which was idealized to the formula mentioned at the beginning.
Cuproiridsite crystallizes in the cubic space group Fd3m(spaceno. 227) with lattice parameter a = 9.92 Å as well as 8 formula units per unit cell.
Formation and sites
Cuproiridsite forms in alluvial deposits, where it can occur besides cuprorhodsite and malanite among other things also with bornite, chalcopyrite, cherepanovite, cooperite, erlichmanite, irarsite, iridosmin, isoferroplatinum, kashinite, laurite, native osmium and platinum, rhodium-containing pentlandite and sperrylite.
As a rare mineral formation cuproiridsite could only be proven at a few places, whereas worldwide about 30 localities have been documented so far (as of 2020). Apart from the mentioned type localities at the mountain Filipp on Kamchatka as well as at the Chad and at the Kondjor massif in Khabarovsk, the mineral was found in Russia at further places on Kamchatka, at the Inagli massif also situated in the Aldan highlands of the Republic of Sache, in the Il’chir ophiolite belt in the Sayan mountains, in a placer deposit on the Is River near Nizhnyaya Tura, and in various ophiolite deposits in the vicinity of Alapaevsk in the Sverdlovsk oblast, as well as in the Ir-Rh-Ni sulfide deposits Centralnoye-I and -II near Rai-Iz (Raiz) in the Tyumen oblast in the Urals.
In Austria cuproiridsite is known so far only from Kraubath on the Mur, from the Sommergraben and from an unnamed chromite deposit on the Mitterberg near Sankt Stefan ob Leoben in Styria.
Other localities include Australia, Canada, Finland, Greece, Italy, Kazakhstan, Cuba, Myanmar, northern Macedonia, the Philippines, Sierra Leone, and the United States of America (Alaska).
- List of minerals
- Н. С. Рудашевский, Ю. П. Меньшиков, А. Г. Мочалов, Н. В. Трубкин, Н. И. Шумская, В. В. Жданов: Купрородсит CuRh2S4 и Купроиридсит CuIr2S4 – Новые Природные Тиошпинели Платиновых Элементов. In Записки Всесоюзного Минералогического Общества. Vol. 114, No. 2, 1985, pp. 187-195 (Russian, rruff.info [PDF; 927 kB; accessed 25 November 2020] English transliteration: N. S. Rudashevsky, Y. P. Men’shikov, A. G. Mochalov, N. V. Trubkin, N. I. Shumskaya, V. V. Zhdanov: Cuprorhodsite CuRh2S4 and cuproiridsite CuIr2S4 – new natural thiospinels of platinum-group elements. In: Zapiski Vsesoyuznogo Mineralogicheskogo Obshchestva).
- Frank C. Hawthorne, Michael Fleischer, Edward S. Grew, Joel D. Grice, John Leslie Jambor, Jacek Puziewicz, Andrew C. Roberts, David A. Vanko, Janet A. Zilczer: New Mineral Names. In: American Mineralogist. Vol. 71, 1986, pp. 1277-1282 ( English, rruff. info [PDF; 641 kB; accessed 26 November 2020]).
- T. Furubayashi, T. Matsumoto, T. Hagino, S. Nagata: Structural and magnetic studies of metal-insulator transition in thiospinel CuIr2S4. In: Journal of the Physical Society of Japan. Vol. 63, 1994, pp. 3333-3339.
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Malcolm Back, William D. Birch, Michel Blondieau and others:The New IMA List of Minerals – A Work in Progress – Updated: November 2020.(PDF; 3.4 MB) In: cnmnc.main.jp. IMA/CNMNC, Marco Pasero, November 2020, accessed 27 November 2020 (English).
Hugo Strunz, Ernest H. Nickel: Strunz Mineralogical Tables. Chemical-structural Mineral Classification System. 9th edition. E. Schweizerbart’sche Verlagsbuchhandlung (Nägele u. Obermiller), Stuttgart 2001, ISBN 3-510-65188-X, p. 94 ( English).
Cuproiridsite. In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (eds.): Handbook of Mineralogy, Mineralogical Society of America. 2001 (English, handbookofmineralogy.org [PDF; 63 kB; retrieved 27 November 2020]).
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Type Occurrence of Cuproiridsite.In: mindat.org. Hudson Institute of Mineralogy, retrieved 27 November 2020 (English).
Catalogue of Type Mineral Specimens – C.(PDF 131 kB) In: docs.wixstatic.com. Commission on Museums (IMA), 12 December 2018, accessed 27 November 2020.
Ferdinando Bosi, Cristian Biagioni, Marco Pasero: Nomenclature and classification of the spinel supergroup. In: European Journal of Mineralogy. Vol. 31, No. 1, 12 September 2018, pp. 183-192 , doi:10.1127/ejm/2019/0031-2788 [English].
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Frank C. Hawthorne, Michael Fleischer, Edward S. Grew, Joel D. Grice, John Leslie Jambor, Jacek Puziewicz, Andrew C. Roberts, David A. Vanko, Janet A. Zilczer: New Mineral Names. In: American Mineralogist. Vol. 71, 1986, pp. 1277-1282 ( English, rruff. info [PDF; 641 kB; accessed 27 November 2020]).
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