IMA 2018-124 = orthocuproplatinum

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Marco E. Ciriotti
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IMA 2018-124 = orthocuproplatinum

Messaggio da Marco E. Ciriotti » gio 02 mag, 2019 13:57

▪ Cabral, A.R., Skála, R., Vymazalová, A., Maixner, J., Stanley, C.J., Lehmann, B., Jedwab, J. (2019): Orthocuproplatinum, Pt3Cu, a new mineral from the Lubero region, North Kivu, Democratic Republic of the Congo. Mineralogy and Petrology, 113, (in press).

Orthocuproplatinum, Pt3Cu, is a new mineral from the Lubero region of North Kivu, Democratic Republic of the Congo. The mineral, which has a synthetic analogue, occurs as a 1.5-mm-long alluvial grain in a heavy-mineral concentrate, together with the holotype specimen of kitagohaite, Pt7Cu. The grain of orthocuproplatinum has a rim of hongshiite, PtCu, and abundant inclusions of calcite. Opaque and metallic, orthocuproplatinum has a whitish colour in reflected light and slightly perceptible anisotropy. The crystal structure of orthocuproplatinum is orthorhombic, space group Cmmm. Its unit-cell parameters: a = 7.681(1) Å; b = 5.4318(8) Å; c = 2.7502(4) Å; V = 114.74(3) Å3; Z = 2. The calculated density is 17.866 g cm−3. The strongest diffraction lines are [d in Å(I)]: 2.337 (11), 2.236 (100), 2.217 (97), 1.932 (61), 1.920 (30), 1.362 (36), 1.169 (24), 1.161 (23). The Vickers hardness is 243 kg mm−2 (VHN25), corresponding to a Mohs hardness of 4. The empirical formula of orthocuproplatinum, calculated from a mean value of 12 electron-probe microanalyses that gave 12.9 wt% Cu and 87.3 wt% Pt, is Pt2.76Cu1.24 on the basis of 4 atoms.
Marco E. Ciriotti

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