Nipalarsite, Ni₈Pd₃As₄, a new platinum-group mineral from the Monchetundra Intrusion, Kola Peninsula, Russia

Abstract

Nipalarsite, Ni8Pd3As4, is a new platinum-group mineral discovered in the sulfide-bearing orthopyroxenite of the Monchetundra layered intrusion, Kola Peninsula, Russia (67°52′22″N, 32°47′60″E). Nipalarsite forms anhedral grains (5–80 µm in size) in intergrowths with sperrylite, kotulskite, hollingworthite, isomertieite, menshikovite, palarstanide, nielsenite and monchetundtraite enclosed in pentlandite, anthophyllite, actinolite and chlorite. Nipalarsite is brittle, has a metallic lustre and a grey streak. In plane-polarised light, nipalarsite is light grey with a blue tinge. Reflectance values in air (in %) are: 46.06 at 470 nm, 48.74 at 546 nm, 50.64 at 589 nm and 54.12 at 650 nm. Values of VHN20 fall between 400.5 and 449.2 kg.mm–2, with a mean value of 429.9 kg.mm–2, corresponding to a Mohs hardness of ~4. The average result of 27 electron microprobe wavelength dispersive spectroscopy analyses of nipalarsite is (wt.%): Ni 44.011, Pd 28.74, Fe0.32, Cu 0.85, Pt 0.01, Au 0.05, As 25.42, Sb 0.05, Te 0.39, total 99.85. The empirical formula (normalised to 15 atoms per formula unit) is: (Ni8.10Fe0.06)Σ8.16(Pd2.94Cu0.18)Σ3.12(As3.68Te0.03)Σ3.71 or, ideally, Ni8Pd3As4. Nipalarsite is cubic, space group Fm$\bar{3}$m, with a = 11.4428(9) Å, V = 1498.3(4) Å3 and Z = 8. The strongest lines in the powder X-ray diffraction pattern of synthetic Ni8Pd3As4 [d, Å (I) (hkl)] are: 2.859(10)(004), 2.623(6)(313), 2.557(6)(024), 2.334(11)(224), 2.201(35)(115,333), 2.021(100)(044), 1.906(8)(006,244) and 1.429(7)(008). The crystal structure was solved and refined from the single-crystal X-ray diffraction data of synthetic Ni8Pd3As4. The relation between natural and synthetic nipalarsite is illustrated by an electron back-scattered diffraction study of natural nipalarsite. The density calculated on the basis of the empirical formula of nipalarsite is 9.60 g.cm–3. The mineral name corresponds to the three main elements: Ni, Pd and As.

Platinum–group minerals in the placer deposit in northwestern Hokkaido, Japan: description of a new mineral, tomamaeite

“…Tomamaeite in Hokkaido is found only as minute particles in Pt-Fe(Cu) alloys (Fig. 7), and its occurrence is common in many localities (e.g., Orsoev et al, 2001;Grokhovskaya et al, 2005Grokhovskaya et al, , 2009Kozlov et al, 2011;Tolstykh et al, 2015;Grokhovskaya et al, 2019;Kuzmin et al, 2020). Based on these occurrences, tomamaeite is thought to occur by decomposition of Pt-Fe(Cu) alloys such as tulameenite, and its counterpart, the Pt-rich phase, should also occur.…”

“…Cu 3 Pt mineral was originally discovered in replacement rims composed of tulameenite on an isoferroplatinum core as a fine inclusion with diameters up to several tens of micrometers (Distler et al, 1986) and was subsequently reported to have similar occurrence in various localities (e.g., Orsoev et al, 2001;Grokhovskaya et al, 2005Grokhovskaya et al, , 2009Kozlov et al, 2011;Tolstykh et al, 2015;Grokhovskaya et al, 2019;Kuzmin et al, 2020). Grigor'eva et al (2018) reported the occurrence of 10 µm intergrowth grains consisting of orcelite, laurite, and Cu 3 Pt mineral in chromitite.…”

Tomamaeite Cu3Pt in native osmium from river sediments in the Nizhnie Sergi Region, Central Urals

“…До утверждения минерала фаза состава Cu 3 Pt изредка отмечалась в ассоциациях минералов элементов платиновой группы (ЭПГ) из хромититов и других пород зональных базит-ультрабазитовых комплексов урало-аляскинского типа и в связанных с ними россыпях (Дмитренко и др., 1985;Дистлер и др., 1986;Tolstykh et al, 2002;Козлов и др., 2011, Степанов, 2015. На данный момент достоверно известны следующие проявления томамаэита: береговые и речные россыпи в районе Томамаэ (всего восемь россыпей) (Nishio-Hamane, Saito, 2020;, Гальмоэнанский массив, Камчатка (Власов и др., 2002;Козлов и др., 2011;Tolstykh et al, 2004), Нижнетагильский массив, Средний Урал (Козлов и др., 2011;Tolstykh et al, 2015), массив Вересовый Бор, Средний Урал (Степанов и др., 2020), Красногорский и Матыскенский массивы, Корякское нагорье (Дмитренко и др., 1985;Дистлер и др., 1986;, массив Кондёр, Алданский щит (Рудашевский и др., 1992), массив Наган, Западная Монголия (Агафонов, Леснов, 1997), и Оспинско-Китойский массив, Восточный Саян (Orsoev et al, 2000;Орсоев и др., 2001;Григорьева и др., 2018), Бураковский расслоенный комплекс, Северная Карелия (Гроховская и др., 2005), массив Мончетундра, Кольский полуостров (Гроховская и др., 2005;Grokhovskaya et al, 2019) и массив Желтая Сопка, Северный Урал (Кузьмин и др., 2020).…”