Canadian Mineralogist Vol. 12, pp. 426 (1974)

A FURTIIER OCCURRENCE OF RUTIIENIRITX)SMII\E

K. G. SNETSINGER SpaceScience Division, Ames ResearchCenter, National Aeronautics and Space Administratlon, Moffett Field, California 94035

INrnopuctron Pd 4.0, Rh 2.3, Au 0.4 and Pt 2.5 weight per cent, summation 101.3. The formula on the In a paper dealing with nomenclature of na- basis of two metal atoms per unit cell is Rur.zr tural phases in the ternary -- Oso.aelro.zoPdo.roRho.ouPto.oa.Auo.or.Optical proper- (1973) aloy system, Harris & Cabri ties are in qualitative agreement with the data defined rutheniridosmine as a new Os-Ir-Ru given by Harris & Cabri (1973) and Stumpfl & group having Os less than 80 atomic Tarkian (1973). X-ray powder data show the per cent of (Os+Ir+Ru), and Ru 10 to 80 mineral is isomorphous with pure osmium and atomic per cent of (Os*Ir*Ru), no single ele- ruthenium metals, the cell edge values (a 2.713 ment being more abundant than 1O atomic per -t0.001, c 4.30110.002) and d-spacingsbe- cent of the total metals. Rutheniridosmine is ing somewhat more comparable to pure ruthe- hexagonal; its crystallographic and chemical nium. relationships to other Os-Ir-Ru alloys are best This mineral contains appreciably more Ru seenin Figure 4 of Harris & Cabri (1973). These than the rutheniridosmines cited by Harris & authors analyzed rutheniridosmine from Can- Cabri (1973), and more of this element than the ada, South America, Papua and New Guinea. alloy occurrences analyzed by Stumpfl & Tar- The present note records a Russian occulrence kian (1973). It would thus seem to be the most of this new mins14l, an example of a very ruthe- ruthenium-rich alloy so far described. At the nium-rich alloy in the series. same time it contains sufficient osmium as to The rutheniridosmine-bearing sample has approach very closely indeed the composition of collection number 15182 in the California Div- osmian ruthenium, another new mineral group ision of Mines Mineralogy Collection; it is a defined by Harris & Cabri (L973). noble-metal placer paysand labelled "Demidoff Estate, Central Urals". Grains are angular and REFERENCES equant, ranging in size from a few microns to 1.5 mm in diameter. Although individual par- Hennrs, D. C. & Cernr, L. I. (1973): The nomen- ticles are homogeneous,grain-to-grain Ru con- clature of the natural alloys of osmium, iridium tent ranges {rom 1Oto 50 weight per cent, with and ruthenium based on new compositional data of alloys from world-wide occurrences, Can. corresponding variation in (Os*Ir). The frag- Mineral, 12, lO4-1L2. ment analyzed was roughly ellipsoidal and 180 Sruurrr-, E. F. & TenneN, M. (1973): Natural os- microns in length. Electron probe analysis, using mium-iridium alloys and -bearing plathum: puro elements and alloys as standards, and ap- new electron probe and optical data. N. lb. Min- plying all instrumental and matrix-effect correc- eral. Mh. 7-8, 313-322. tions to the data, gave Ru 47,9, Os 29.2, h 15.O, Manuscript received March 1974.

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