Nickolayite, FeMoP, a new natural molybdenum phosphide

Mikhail N. Murashko, Sergey N. Britvin, Yevgeny Vapnik, Yury S. Polekhovsky, Vladimir V. Shilovskikh, Anatoly N. Zaitsev, Oleg S. Vereshchagin

Research output: Contribution to journalArticlepeer-review

Abstract

Nickolayite, FeMoP, is a new terrestrial phosphide structurally related to allabogdanite (highpressure modification of (Fe,Ni)2P), meteoritic phosphides florenskyite, FeTiP and andreyivanovite, FeCrP. From the point of view of chemical composition, nickolayite is a Fe-analogue of monipite, MoNiP. The mineral was discovered in the Daba-Siwaqa complex (Central Jordan), a part of the pyrometamorphic Hatrurim Formation (the Mottled Zone), whose outcrops encompass a 150×200 km2 area around the Dead Sea in the Middle East. Nickolayite appears as an accessory phase in the fused clinopyroxene-plagioclase rocks texturally resembling gabbro-dolerite. The irregularly shaped grains of the mineral, up to 80 μ m in size are associated with baryte, tridymite, chromite, hematite, pyrrhotite, fluorapatite, titanite, and powellite. Macroscopically, nickolayite grains possess lightgrey to greyish-white colour and metallic lustre. The mineral is ductile. The mean VHN hardness (50 g load) is 538 kg mm-2. The calculated density based on the empirical formula and the unit-cell parameters is 7.819 g cm-1. In reflected light, nickolayite has white colour, with no bireflectance and pleochroism. The COM approved reflectance values [Rmax/Rmin (%), ?(nm)]: 48.5/46.5 (470), 50.5/48.5 (546), 51.8/49.9 (589), 53.9/52.0 (650). Chemical composition of the holotype crystal (electron microprobe, average of 4 analyses, wt.%): Fe 32.21, Mo 47.06, Ni 3.69, Co 0.13, P 17.45, Total 100.54, that corresponds to the empirical formula Fe1.00(Mo0.87Ni0.11Fe0.02)1.00P1.00 and an ideal formula of FeMoP. Nickolayite is orthorhombic, space group Pnma, unit-cell parameters of holotype material: a 5.9519(5), b 3.7070(3), c 6.8465(6) , V = 151.06(2) 3 and Z = 4. The crystal structure of holotype material was solved and refined to R1 = 0.0174 based on 251 unique observed reflections. The origin of the mineral is likely connected to the processes of co-reduction of molybdenum- and phosphorus-bearing minerals during high-temperature pyrometamorphic processes.

Original languageEnglish
JournalMineralogical Magazine
DOIs
StateAccepted/In press - 1 Jan 2022

ASJC Scopus subject areas

  • Geochemistry and Petrology

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