I doubt many is a old news, seen the found have presented in the last Met.Society Meeting
A NEW IRON-NICKEL PHOSPHIDE FROM THE NORTHWEST AFRICA 1054 METEORITE. V. Moggi-Cecchi1, L.Bindi2, and G. Pratesi2,3, 1Museo di Scienze Planetarie, Provincia di Prato, Via Galcianese, 20/h, I-59100 Prato, Italy, 2Museo di Storia Naturale, Università degli Studi di Firenze, I-50121 Firenze, Italy, 3Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira, 4, I-50121, Florence, Italy Introduction: NWA 1054 is a primitive achondrite (acapulco-ite) with a main mass weighing 86 g. The thin section displays a granular texture with olivine and low-Ca pyroxene as major phases and high Ca-pyroxene and plagioclase as minor; major non-silicate phases are metal and troilite. Accessory phases include merrillite, a Mg-rich chromite and two iron-nickel phosphides. Terrestrial weathering grade is low (W1) as well as shock stage (S1). The Museo di Scienze Planetarie of Prato (MSP) owns the type speci-men (MSP2366) [1]. Description: Six natural phophides are known: schreibersite, (Fe,Ni,)3P, nickelphosphide (Ni,Fe)3P [2], barringerite (Fe,Ni)2P [3], allabogdanite (Fe,Ni)2P [4], florenskyite FeTiP [5] and perry-ite, (Ni,Fe)8(Si,P)3 [6]. In the course of a study on some acapulco-ites a new rather common iron-nickel phosphide was discovered in the NWA 1052 and 1054 acapulcoites [7]. The chemical composi-tion of the new phase, determined by EMPA, is (Ni2.30Fe1.64Co0.01)Σ=3.95P1.05, pointing to a 4:1 metal/phosphorous ratio. It occurs as anhedral grains up to 100 μm either associated with kamacite (Fig. 1A) or with nickelphosphide (Fig. 1B). Micro-indentation measurements provided a value (447 kg/mm2) lower than nickelphosphide. In reflected light, the new phase is cream-yellowish, non pleochroic, isotropic, and shows no bireflectance, without internal reflections. Reflectance values are 60.56, 50.44 52.51 and 55.94 % at 471.1, 548.3, 586.6, and 652.3 nm, respec-tively. A single-crystal X-ray diffraction study, carried out on a small crystal fragment, indicates a cubic lattice with a = 6.025 ± 0.001 and points to a space group P213 with Z = 4. Both the coor-dination-number (12) and the density (7.882 g/cc) are the highest ever reported for phosphorus and iron-nickel phosphides, respec-tively. Conclusions: The structure and the physical properties suggest that the new iron nickel phosphide could play an important role for Earths core mineralogy. Due to the presence of this phase NWA 1054 acapulcoite seems to be a really peculiar acapulcoite if com-pared with literature data [8-9]. References: [1] Moggi Cecchi V. & Pratesi G. (2005) MAPS, 40, in press [2] Skála R. & Drábek M. (2003) Min. Mag. 67, 783 [3] Buseck P.R. (1969) Science 165,169 [4] Britvin S.N. et al., (2002) Am. Min.. 87, 1245 [5] Ivanov A.V. et al., (2000) Am. Min. 85, 1082 [6] Okada A. et al. (1988) MAPS 23, 59 [7] Moggi-Cecchi V., Pratesi G., Mancini L., (2005) LPSC. XXXVI, abs. #1808 [8] Patzer A., Hill D.H., Boynton W.V. (2004) MAPS 39, 61 [9] Scott E.R.D. & Pinault, L.J. (1999) LPSC. XXX, abs. #1507. Matteo --- Göran Axelsson <[EMAIL PROTECTED]> ha scritto: > What is the big news? > > Merrillite (Ca3(PO4)2) is found in several > meteorites. From martian > meteorites () to pallasites (Springwater). Another > meteorites containing > merrillite are Portales Valley, Forest Vale, > Ankober, Allegan, Allegan, > Estacado, and several more. > > And among the acapulcoites are Dhofar 1222. > > It doesn't seem to be such a rare phosphate to me. > > /Göran > > M come Meteorite Meteorites wrote: > > >Hello > > > >Today in the Museo di Scienze Planetarie of Prato > it > >comes presented the new Iron-Nichel posphide found > in > >my acapulcoite NWA 1054. The official name of the > >posphide its melliniite. > > > >Matteo > > > > > >M come Meteorite - Matteo Chinellato > >Via Triestina 126/A - 30030 - TESSERA, VENEZIA, > ITALY > >Email: [EMAIL PROTECTED] > >Sale Site: http://www.mcomemeteorite.it > >Collection Site: http://www.mcomemeteorite.info > >MSN Messanger: spacerocks at hotmail.com > >EBAY.COM:http://members.ebay.com/aboutme/mcomemeteorite/ > > > > > > > > > > > > > >___________________________________ > >Yahoo! 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