Murashkoite, FeP, a new terrestrial phosphide from pyrometamorphic rocks of the Hatrurim Formation, South Levant

Murashkoite, FeP, is a new mineral found in pyrometamorphic rocks of the Hatrurim Formation, South Levant. It is a typical accessory phase in the marbles and paralavas in the southern Negev Desert, Israel and on the Transjordan Plateau, Jordan. Murashkoite occurs as grains and aggregates up to 2mm closely associated with barringerite, (Fe,Ni)(2)P, and zuktamrurite, FeP2. The rock-forming minerals include pyroxenes of the diopside-hedenbergite series, anorthite with subordinate gehlenite, tridymite, cristobalite, pyrrhotite, fluorapatite, chromite, magnetite, hematite, merrillite and late hydrothermal carbonates, silicates and sulfates. Macroscopically, murashkoite is yellowish-grey in colour and has a metallic lustre. In reflected light, the mineral is white with a beige tint and it is non-pleochroic. The anisotropy is distinct, from yellow-grey to greyish-blue. Selected reflectance values [R-max-R-min, % (, nm)] are: 42.7-40.8 (400), 42.0-40.6 (500), 44.5-43.4 (600), 48.0-47.7 (700). It is brittle. VHN20=468kgmm(-2). The holotype material has the chemical composition (electron microprobe): Fe 63.82; Ni 0.88; P 35.56; total 100.26wt.%. The empirical formula calculated on the basis of 2 apfu is (Fe0.99Ni0.01)(1.00)P-1.00 corresponding to FeP. Murashkoite is orthorhombic, space group Pnma, unit cell parameters refined from the single-crystal data are: a 5.099(2), b 3.251(2), c 5.695(2) angstrom, V 94.41(8) angstrom(3), Z=4, D-x=6.108(5) g cm(-3). The crystal structure was solved and refined to R-1=0.0305 on the basis of 131 unique reflections with I>2 sigma(I). The strongest lines of the powder X-ray diffraction pattern [(d, angstrom) (I, %) (hkl)]: 2.831(75)(002,011); 2.548(22)(200); 2.477(46)(102,111); 1.975(47)(112); 1.895(100)(202,211); 1.779(19)(103); 1.632(45)(013,301,020). The mineral is named in honour of Dr. Mikhail Nikolaevich Murashko (born 1952), for his contributions to the mineralogy of the Hatrurim Formation. Murashkoite is a natural counterpart of synthetic FeP, the compound widely used in heterogeneous catalysis and electrocatalysis.