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Zaccariniite, RhNiAs, a new platinum-group mineral from Loma Peguera, Dominican Republic

Anna Vymazalova, Frantisek Laufek, Milan Drabek, Chris J. Stanley, Ronald J. Baker, Raul Bermejo, Giorgio Garuti, Oscar Thalhammer, Joaquin A. Proenza and Francisco Longo
Zaccariniite, RhNiAs, a new platinum-group mineral from Loma Peguera, Dominican Republic
The Canadian Mineralogist (October 2012) 50 (5): 1321-1329


Zaccariniite, RhNiAs, is a new platinum-group mineral discovered in the Loma Peguera ophiolitic chromitite, Dominican Republic. The mineral forms anhedral grains (1-20 mu m in size) and occurs intergrown with garutiite, in association with hexaferrum, Ru-Os-Ir-Fe alloys, Ru-Os-Ir-Fe oxygenated compounds, and chromite. Zaccariniite is opaque and has a metallic luster and a grey streak. The mineral is brittle, with no cleavage. Values of VHN (sub 5) (10 indentations on different grains of synthetic RhNiAs) fall between 166 and 286 kg/mm (super 2) , with a mean value of 218 kg/mm (super 2) , corresponding to a Mohs hardness of approximately 3.5-4. Under plane-polarized reflected light, the mineral is white with brownish to pinkish tints, has moderate to strong bireflectance, a strong white to pinkish brownish white pleochroism, and strong anisotropy, with rotation tints from orange to blue-green; it exhibits no internal reflections. Reflectance values of zaccariniite in air (R1, R2 in %) are: 49.4, 49.4 at 470 nm; 52.4, 53.2 at 546 nm; 54.2, 53.2 at 589 nm; and 56.6, 53.3 at 650 nm. Three electron microprobe analyses of natural zaccariniite gave an average composition of: Rh 41.77, Os 0.51, Ir 0.64, Ru 0.46, Pd 0.34, Ni 23.75, Fe 0.53, As 27.84, S 0.10, for a total of 96.09 wt.%, corresponding to the empirical formula (Rh (sub 1.01) Os (sub 0.01) Ir (sub 0.01) Ru (sub 0.01) Pd (sub 0.01) ) (sub Sigma 1.05) (Ni (sub 1.00) Fe (sub 0.02) ) (sub Sigma 1.02) (As (sub 0.92) S (sub 0.01) ) (sub Sigma 0.93) based on three atoms. The average result of twenty-eight analyses of synthetic zaccariniite is: Rh 44.57, Ni 24.50, and As 31.82 total 100.88 wt.%, corresponding to Rh (sub 1.02) Ni (sub 0.98) As (sub 1.00) . The mineral is tetragonal, belongs to space group P4/nmm with lattice parameters a = 3.5498(1), c = 6.1573(2) Aa, V = 77.59(1) Aa (super 3) , Z = 2, and crystallizes with the Cu (sub 2) Sb structure type. The strongest lines in the X-ray powder-diffraction pattern of synthetic zaccariniite [d in Aa(I)(hkl)] are: 2.5092(40)(110), 2.3252(100)(111,102), 1.9453(51)(112), 1.7758(80)(103,200), 1.2555(40)(213,220), 1.1044(22)(302,311), 1.0547(23)(312), 0.9730(42)(215). The new Rh-Ni arsenide is named after Federica Zaccarini in recognition of her important contributions to the mineralogy of platinum-group elements.

ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 50
Serial Issue: 5
Title: Zaccariniite, RhNiAs, a new platinum-group mineral from Loma Peguera, Dominican Republic
Affiliation: Czech Geological Survey, Prague, Czech Republic
Pages: 1321-1329
Published: 201210
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 21
Accession Number: 2013-010797
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 7 tables
N17°30'00" - N20°00'00", W72°00'00" - W68°19'60"
Secondary Affiliation: Natural History Museum, GBR, United KingdomMontanuniversitaet Leoben, AUT, AustriaUniversity of Barcelona, ESP, SpainFalcondo Xstrata Nickel, DOM, Dominican Republic
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201308
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