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This paper describes a multi-technique approach to the complete crystal-chemical characterization of a gadolinite-(Y) sample found in a volcanic holocrystalline ejectum near the Vico lake (Latium, Italy). Gadolinite-(Y) occurs as poly-twinned crystals forming rounded short-prismatic aggregates (generally 0.1-0.3 mm in size, with the largest ever found >1 mm), associated with zircon, thorite, danburite, betafite, and tourmaline. Both the chemical and the structural characterization of gadolinite-(Y from Vico required nonstandard procedures. After correction for (100) twinning, the structure of a crystal with unit-cell dimensions a = 4.7708(4) [Angstrom], b = 7.6229(7) [Angstrom], c = 9.8975(9) [Angstrom], [beta] = 90.017(7)[degrees], and V = 359.95(6) [[Angstrom].sup.3] was refined in the [P2.sub.1]/c space group down to R = 2.3%. Electron microprobe (EMP) analyses failed to give accurate quantification of major elements, due to the presence of light and volatile elements as well as of rare earth elements (REE) and actinides. Secondary ion-mass spectrometry (SIMS) analysis done with accurate calibrations on well-characterized minerals allowed quantification of light, volatile, REE, and actinide elements, and also of Ca and Si. The derived chemical composition was interpreted with reference to the site-scattering values obtained from single-crystal structure refinement. The resulting unit formula is [([Ca.sub.0.81][REE.sub.0.66][Y.sub.0.39][Th.sub.0.13] [U.sub.0.02]).sub.[SIGMA]2.01][([Fe.sup.2+.sub.029][Li.sub.0.14] [([Fe.sup.3+.sub.0.12][Mn.sub.0.02][Mg.sub.0.01]).sub.[SIGMA]0.58] [([Si.sub.1.98][Be.sub.1.09][B.sub.0.81][Li.sub.0.12]).sub.[SIGMA]4.00] [O.sub.8][([O.sub.1.20][F.sub.0.51][OH.sub.0.29]).sub.[SIGMA]2.00], which yields a calculated density of 4.267 g [cm.sup.-3]. Fourier transform infrared spectroscopy (FTIR) single-crystal spectrum of gadolinite-(Y) shows several absorptions in the OH-stretching region that can be assigned to the different local configurations involving Ca and (REE,Y) at the A site and Be, B, and Li at the Z site. Lithium incorporation in gadolinite-group minerals is proposed to occur according to the exchange vectors: (1) [sup.X][Fe.sup.2+] + [sup.A]Y [right arror] [sup.X]Li + [sup.A](Th + U) and (2) [sup.Z]Be + [sup.X][Fe.sup.2+] [right arrow] [sup.Z]Li + [sup.X][Fe.sup.3+]; the maximum amount of Li allowed in the gadolinite structure is 1.0 apfu. This work provides the first evidence that Li is a significant component in gadolinite-group minerals, particularly in geochemical environments enriched in actinides. This conclusion suggests that materials having the composition of Li-rich gadolinite may be considered as possible forms for radioactive waste disposal. Keywords: Gadolinite, lithium, single crystal XRD, EMPA, SIMS, IR spectroscopy

Direct structural characterization of the changes in the local environment of Mg occurring in the garnet structure as a function of the Ca content are determined by Mg K-edge X-ray absorption fine structure on synthetic samples along the pyrope-grossular join. With increasing Ca content, the short Mg-O2 distance of the dodecahedron slightly decreases, while the long Mg-O4 distance tends to increase, so that the dodecahedron is more distorted in grossular-rich garnets than in end-member pyrope. This quantitative direct description of the changes in the local environment of Mg in the pyrope-grossular solid solution confirms and better defines previous experimental and recent computational results. Keywords: Pyrope-grossular garnets, EXAFS, magnesium, local environment

Here we present [sup.45]Sc and [sup.27]Al NMR results on Sc-doped pyrope ([Mg.sub.3][Al.sub.2][Si.sub.3][O.sub.12]), grossular ([Ca.sub.3][Al.sub.2][Si.sub.3][O.sub.12]), and an 80% grossular-20% pyrope garnet (grs80) that have recently been well-studied by X-ray diffraction and X-ray spectroscopies. Clearly distinct NMR peaks are observed for Sc in the eight-coordinated X site (pyrope and grs80) and in the six-coordinated Y site (grossular and grs80). X-ray and NMR data agree that only eight-coordinated Sc is present in pyrope and that six-coordinated Sc is predominant in grossular; however, the XRD results also indicated significant X and Z site (four-coordinated) Sc in the Ca-rich garnet. Possible reasons for this apparent discrepancy are discussed. We demonstrate that [sup.45]Sc NMR is potentially a useful new method for studies of the site occupancies of [Sc.sup.3+] in oxides and silicates, at least in experimental systems where its concentration is a few percent or greater. Keywords: Crystal structure, pyrope-grossular garnet, scandium in garnet, NMR spectroscopy, pyrope-grossular garnet, scandium-45, aluminum-27

This paper reports a single-crystal unpolarized-light FTIR study in the OH-stretching region of a suite of well-characterized Ti-rich pargasites from Lherz (French Pyrenees). All amphiboles studied have fairly constant M-site composition, with [sup.[6]][Al.sub.tot] ~0.55 atoms per formula unit (apfu), [sup.[6]]Ti ~0.45 apfu, and [sup.[6]][Fe.sup.3+] ~0.40 apfu. SIMS and SREF data show all samples to have an O3 anion composition of OH [approximately equal to] [O.sup.2-] [approximately equal to] 1.0 apfu, with negligible F. The FTIR spectra show for all samples a broad absorption consisting of several overlapping bands; three main components can be recognized: ~3710, 3686, and 3660 [cm.sup.-1], respectively, with an asymmetric tail extending to lower frequency. Six Gaussian components can be fitted to the spectra; comparison with spectra of both synthetic and natural pargasites allows five of these components to be assigned to local configurations involving OH-[O.sup.2-] at the O3 site, thus showing that coupling with an [O.sup.2-] anion through an A-cation significantly affects band position. Infrared spectroscopy can detect the presence of [O.sup.2-] in amphiboles in chemically favorable cases, i.e., in the absence of F. Moreover, the FTIR spectra show that all octahedral configurations involving [sup.M1][Ti.sup.4+] or [sup.M1][Fe.sup.3+] [sup.M3][Fe.sup.3+] are associated with [O.sup.2-] at both adjacent O3 sites, and that [sup.M3]Al is locally associated with OH, confirming SRO models based on structure refinement results. Keywords: Ti-rich pargasite, Lherz (French Pyrenees), single-crystal FTIR spectroscopy, anion occupancy

Aluminotaramite, ideally Na(CaNa)([Fe.sup.2+.sub.3][Al.sub.2]) ([Si.sub.6][Al.sub.2])[O.sub.22][(OH).sub.2], and alumino-magnesiotaramite, ideally Na(CaNa)([Mg.sub.3][Al.sub.2]) ([Si.sub.6][Al.sub.2])[O.sub.22][(OH).sub.2], occur in retrogressed eclogites in the Liset kyanite-eclogite pod, near Selje, Vestlandet, Norway. Fluoro-alumino-magnesiotaramite, ideally Na(CaNa)([Mg.sub.3][Al.sub.2]) ([Si.sub.6][Al.sub.2])[O.sub.22][F.sub.2], occurs in the Jianchang eclogite, Su-Lu coesite-eclogite province, China. These aluminotaramites always replace other higher pressure amphiboles (nyboite and fluoronyboite), and their higher Al content derives from resorbed garnets and lowered pressure during retrogression from the eclogite to the amphibolite facies. This paper reports complete mineral data for the three new holotypes as obtained by EMP analysis, structure refinement, and optical measurements. The three new minerals and mineral names have been approved with votes 2006-023, 2006-024, and 2006-025, respectively, by the IMA Commission on New Minerals, Nomenclature and Classification. Holotype aluminotaramite has the unit formula: [sup.A][([Na.sub.0.89] [K.sub.0.01).sub.[SIGMA]0.90] [sup.B][(Fe.sup.2+.sub.0.11][Na.sub.0.82][Ca.sub.1.07]).sub.[SIGMA]2.00] [sup.C][([Fe.sup.2+.sub.1.75] [Mg.sub.1.62][Al.sub.1.12][Fe.sup.3+.sub.0.42][Ti.sub.0.07][Zn.sub.0.01] [Mn.sub.0.01]).sub.[SIGMA]5.00] [sup.T][([Si.sub.6.23][Al.sub.1.77]).sub.[SIGMA]8.00][O.sub.22] [sup.W] [(O[H.sub.1.86][F.sub.0.14]).sub.[SIGMA]2.00], and a = 9.7489(5), b = 17.9377(7), c = 5.3233(3) [Angstrom], [beta] = 104.539(5)[degrees], V = 901.1(2) [[Angstrom].sup.3]; the calculated density is 3.29 g/[cm.sup.3]. Holotype alumino-magnesiotaramite has the unit formula: [sup.A] [Na.sub.1.07] [sup.B][([Fe.sup.2+.sub.0.06][Na.sub.0.73][Ca.sub.1.21]).sub.[SIGMA]2.00] [sup.C][([Fe.sup.2+.sub.1.06] [Mg.sub.2.40][Al.sub.1.20][Fe.sup.3+.sub.0.31] [Ti.sub.0.03]).sub.[SIGMA]5.00] [sup.T][([Si.sub.6.09][Al.sub.1.91]).sub.[SIGMA]8.00] [O.sub.22] [sup.W] [(OH).sub.2.00] and a = 9.7899(7), b = 17.8991(9), c = 5.3192(5) [Angstrom], [beta] = 104.900(7)[degrees], V = 900.7(3) [[Angstrom].sup.3]; the calculated density is 3.21 g/[cm.sup.3]. Holotype fluoro-alumino-magnesiotaramite has the unit formula: [sup.A] [Na.sub.0.99] [sup.B][([Fe.sup.2+.sub.0.02][Na.sub.0.77][Ca.sub.1.21]).sub.[SIGMA]2.00] [sup.C][([Fe.sup.2+.sub.1.11] [Mg.sub.2.12][Al.sub.1.04][Fe.sup.3+.sub.0.68][Ti.sub.0.03] [Mn.sub.0.02]).sub.[SIGMA]5.00] [sup.T][([Si.sub.6.00][Al.sub.2.00]).sub.[SIGMA]8.00] [O.sub.22] [sup.W][([F.sub.1.04]O[H.sub.0.96]).sub.2.00], and a = 9.7414(8), b = 17.9095(13), c = 5.3335(4) [Angstrom], [beta] = 104.672(1)[degrees], V = 900.2(3) [[Angstrom].sup.3]; the calculated density is 3.26 g/[cm.sup.3]. Keywords: Aluminotaramite, alumino-magnesiotaramite, fluoro-alumino-magnesiotaramite

A systematic chemical and structural investigation of arrojadite-group minerals has provided new data allowing us to design a consistent nomenclature scheme, approved by the IMA CNMMN (vote 05-D). The cornerstones of this scheme are: (1) the fundamental structural formula for the arrojadite group is [A.sub.2] [B.sub.2] Ca [Na.sub.2+x] [M.sub.13] Al [(P[O.sub.4]).sub.11] (P[O.sub.3]O[H.sub.1-x]) [W.sub.2], where A are either large divalent cations (Ba, Sr, Pb) plus vacancy, or monovalent (K, Na) cations, B are either small divalent cations (Fe, Mn, Mg) plus vacancy, or monovalent (Na) cations. (2) The dominant cation at the M sites defines the rootname: [Fe.sup.2+], arrojadite; [Mn.sup.2+], dickinsonite; Mg (if any), name to be proposed. (3) Two suffixes are added to the root-name according to the dominant cation of the dominant valence state at the A1 and B1 sites (the mono- or divalent nature of the cation used implicitly specifies the dominant occupancy by Na or the dominant vacancy, respectively, at the A2 and B2 sites, according to two heterovalent substitutions). (4) A third suffix is added in case the sum of non-(P,A1) cations exceeds 20.5 apfu [which implies that the Na3 site is more than half occupied and the total (OH,F) content is less than 2.5 apfu]. (5) Prefixes may be added to the root-name in the case of dominance of F over OH at the W site or of [Fe.sup.3+] over Al at the Al site. The compositional range explored is quite large, with either K, Sr, Ba, or Pb as the dominant cation at A1; Na, Fe, or Mn dominant at B1; Na or vacancies dominant at A2 and B2; Na or vacancy at the Na3 site; and F or OH at the W site. Lithium can amount up to 1 Li pfu and is partitioned into the M sites, preferentially M1. As a consequence of this new nomenclature scheme, the mineral name 'sigismundite' is abolished and the corresponding composition must be referred to as arrojadite(BaFe). In addition, arrojadites--dickinsonites from classic localities are identified as arrojadite-(KFe) (Nickel Plate Mine), dickinsonite-(KMnNa) (Branchville), fluorarrojadite-(BaFe) (Sidi-bou-Kricha), and we define the new members arrojadite-(KNa) (Rapid Creek), arrojadite-(PbFe) (Sapucaia), and arrojadite-(SrFe) (Horrsjoberg). Keywords: Crystal structure, arrojadite, analysis, chemical (mineral), new minerals, arrojadite(PbFe), fluorarrojadite-(BaFe), arrojadite-(BaFe), optical properties, XRD data.

A re-examination of the chemistry and structure of nearly all the known occurrences of arrojadite and related minerals (dickinsonite and sigismundite) allowed understanding of the main substitution vectors and cation ordering schemes ruling the crystal-chemistry of these very complex phosphates. Electron microprobe analyses were done with a careful choice of the standards and of experimental conditions, and were coupled with LA-ICP-MS in situ analysis for Li, Be, and B. Structure refinement was done in a space group (Cc) with a lower symmetry than those used in previous studies (C2/c and its equivalents), which allowed a better understanding of the structure details and of cation ordering. The combined approach yielded a new formula for the arrojadite group, namely [A.sub.2][B.sub.2][Ca.sub.1] [Na.sub.2+x][M.sub.13]Al[(P[O.sub.4]).sub.11] (P[O.sub.3]O[H.sub.1-x]) [W.sub.2], where A are either large divalent cations (Ba, Sr, Pb) plus vacancy, or monovalent (K, Na) cations; and B are either small divalent cations (Fe, Mn, Mg) plus vacancy, or monovalent (Na) cations. The number of hydroxyl groups in the arrojadite formula is generally 3 apfu, and can be lowered to 2 apfu in particular when the sum of non-(P,Al) cations is higher than 20 apfu. We present in this paper the complete characterization of three samples (two of which are new members) that are crucial to fix the cornerstones of arrojadite crystal-chemistry. The sample from Rapid Creek (Yukon Territory) is the holotype for arrojadite-(KNa), and has unit formula [K.sub.0.83][Na.sub.5.01] [([Ca.sub.0.91][Sr.sub.0.01]).sub. [SIGMA]=0.92][([Fe.sup.2+.sub.9.34][Mg.sub.2.69][Mn.sup.2+.sub.1.03] [Zn.sub.0.01][Li.sub.0.01]).sub.[SIGMA]=13.08][([Al.sub.1.04] [Ti.sub.0.02]).sub.[SIGMA]=1.06][(O[H.sub.1.97][F.sub.0.03]).sub. [SIGMA]=2.00][([P.sub.11.99][Si.sub.0.01][T.sub.1])[O.sub.47] [(OH).sub.1.00] [ideally, [sup.A1]K [sup.A2]Na [sup.B1]Na [sup.B2]Na [sup.Na1,2][Na.sub.2] [sup.Na3][] [sup.Ca] Ca [sup.M][Fe.sub.13] Al [(P[O.sub.4].sub.11]) [sup.Plx] (P[O.sub.3]OH) [sup.W][(OH,F).sub.2]] and unit-cell dimensions: a = 16.5220(11), b = 10.0529(7), c = 24.6477 (16) [Angstrom], [beta] = 106.509(2)[degrees], V = 3932.2(7) [[Angstrom].sup.3] (Z = 4). The sample from Horrsjoberg (Varmland, Sweden) is the holotype material for arrojadite-(SrFe), and has unit formula [[Sr.sub.0.93][Na.sub.3.20]([Ca.sub.0.59][Ba.sub.0.20] [Pb.sub.0.03][K.sub.0.03]).sub.[SIGMA]=0.85][([Fe.sup.2+.sub.6.64] [Mg.sub.3.61][Mn.sup.2+.sub.3.33][Zn.sub.0.07][Li.sub.0.01]).sub. [SIGMA]=13.66][([Sc.sub.0.04][Al.sub.1.00]).sub.[SIGMA]=1.04] [(O[H.sub.1.10][F.su.0.90]).sub.[SIGMA]=2.00 [[([P.sub.11.95] [Si.sub.0.02]).sub.[SIGMA]=11.97][O.sub.47][(OH).sub.1.00]] [ideally, [sup.A1]Sr [sup.A2][] [sup.B1][Fe.sup.2+] [sup.B2][] [sup.Na1,2] [Na.sub.2] [sup.Na3][] [sup.Ca]Ca [sup.M][Fe.sup.2+.sub.13] Al [(P[O.sub.4]).sub.11] [sup.Plx](P[O.sub.3]OH) [sup.W][(OH,F).sub.2]], and unit-cell dimensions a = 16.3992(7), b = 9.9400(4), c = 24.4434(11) [Angstrom], [beta] = 105.489(1)[degrees], V = 3839.76(46) [[Angstrom].sup.3]. The sample from Branchville (Connecticut) is the holotype material for dickinsonite-(KMnNa), and has unit formula [K.sub.0.50][Na.sub.5.78][([Ca.sub.0.51][Sr.sub.0.05][Ba.sub.0.01] [Pb.sub.0.01]).sub.[SIGMA]=0.58][([Mn.sup.2+.sub.9.70] [Fe.sup.2+.sub.3.72][Li.sub.0.31][Mg.sub.0.06][Zn.sub.0.01]).sub. [SIGMA]=13.80][([Al.sub.0.91][Fe.sup.3+.sub.0.09][Ti.sub.0.01]).sub. [SIGMA]=1.00][(O[H.sub.1.97][F.sub.0.03]).sub.[SIGMA]=2.00] [([P.sub.12.02][Si.sub.0.01]).sub.[SIGMA]=12.03][O.sub.47] [(OH).sub.0.21] [ideally, [sup.A1]K [sup.A2]Na [sup.B1]Mn [sup.B2][] [sup.Na1,2][Na.sub.2] [sup.Na3]Na [sup.Ca]Ca [sup.M][Mn.sub.13] Al [(P[O.sub.4]).sub.11] [sup.Plx] (P[O.sub.4]) [sup.W] [(OH, F).sub.2]] and unit-cell dimensions a = 16.6900 (9), b = 10.1013 (5), c = 24.8752 (13) [Angstrom], [beta] = 105.616(2)[degrees], V = 4038.9(7) [[Angstrom].sup.3]. Keywords: Crystal structure, arrojadite, analysis (chemical), new minerals, arrojadite-(KNa), arrojadite-(SrFe), dickinsonite-(KMnNa), optical properties, Raman spectroscopy, XRD data

We applied different independent techniques (electron microprobe analysis, structure refinement, and X-ray absorption spectroscopy) to unravel the possible mechanisms of Sc incorporation in the pyrope-grossular join. Samples were synthesized at elevated pressure and temperature by adding 5 wt% of [Sc.sub.2][O.sub.3] to selected nominal compositions (pyrope, [pyrope.sub.60][grossular.sub.40], [pyrope.sub.20][grossulars.sub.80], and grossular). In this way, the site of incorporation was not pre-determined, and only depends on the availability of a mechanism for local charge-balance. The EXAFS spectra of the two end-members could be analyzed by a multi-shell fit procedure, whereas the chemical heterogeneity of the Sc-doped solid-solution terms prevented this approach. However, the available information allows detection of different mechanisms of incorporation, which are active as a function of the bulk composition. In pyrope, Sc mainly enters the dodecahedral X site, and the local charge balance is achieved by incorporation of Mg at the adjacent tetrahedral Z site. Local charge-balance requirements suggest that a Z site occupied by Mg bridges two X sites occupied by Sc. When the entrance of Ca provides relaxation of the averaged structure, Sc may enter all the three available cation sites via the coupled heterovalent exchange [sup.X][Sc.sub.1][sup.Z][Sc.sub.1][sup.X][Mg.sub.-1][sup.Z][Si.sub.-1] and the homovalent exchange [sup.Y][Sc.sub.1][sup.Y][Al.sub-1]. In the samples of this work, there is an apparent limit in the Sc incorporation at the Y site, which is in contrast to the favored mechanism of incorporation in Sc-doped andradites. This limit can be explained in terms of relative dimensions of the structural sites when Al is the dominant Y cation. These results must be taken into account when evaluating trace-element behavior in garnets for geochemical purposes. In particular, they explain why [D.sub.Sc] can be treated together with [D.sub.REE] in models based on the elastic strain theory in garnets close to the pyrope composition, but deviate from the parabolic fit in grossular-rich garnets. Keywords: Crystal structure, garnet, trace elements and REE, scandium, XAS, XRD data, crystal synthesis

Investigation of scandium incorporation in garnets along the synthetic [Ca.sub.3][Fe.sup.3+.sub.2][Si.sub.3][O.sub.12]--[Ca.sub.3][Sc.sub.2] [Si.sub.3][O.sub.12] (adr--CaSc) join, based on the same multi-technique approach used in the companion paper (Oberti et al. 2006a), shows that (1) Sc is incorporated exclusively at the Y octahedron; (2) the local coordination of Sc is slightly different in Sc-poor than in Sc-rich compositions (Sc-O = 2.06 [Angstrom] in Ca[Sc.sub.10] vs. 2.10 [Angstrom] in Ca[Sc.sub.30-90]); (3) the local coordination of Ca is also slightly different in Sc-poor than in Sc-rich compositions [Ca1,2-O are 2.34(2) and 2.48(2) [Angstrom] in Ca[Sc.sub.10] and 2.36(2) and 2.50(2) [Angstrom] in Ca[Sc.sub.90], with [DELTA] fixed at 0.14 [Angstrom] in all the samples]; (4) the linear increase of the unit-cell edge along the join derives from multiple changes in the geometry of the different polyhedra and from the rotation of the tetrahedron around the [bar.4] axis ([alpha] rotation), and cannot be modeled from extrapolation of the behavior observed along the [Ca.sub.3][Al.sub.2][Si.sub.3][O.sub.12]--[Ca.sub.3][Fe.sup.3+.sub.2] [Si.sub.3][O.sub.12] (grs--adr) join. CaSc-rich garnets, where a large X dodecahedron coexists with a large Y octahedron and a Z tetrahedron occupied by Si, similar to pyrope-grossular garnets, have the highest [alpha] values observed to date in calcium silicate garnets. Slightly lower [alpha] values are observed in pyrope and almandine, but correspond to a different structural arrangement, where a small X dodecahedron coexists with a small Y octahedron. These results further confirm the efficiency of a combined short- and long-range approach for understanding the properties of garnet solid solutions. Keywords: Crystal structure, garnet, XAS, XRD data, trace elements and REE, scandium, crystal synthesis

This work reports the crystal-chemical characterization of Mn-rich amphiboles from the Grenville Marble of the Arnold mine, Fowler, St. Lawrence Co., New York (U.S.A.), which were previously described by Benimoff et al. (1991) as 'manganoan silicic edenite.' According to the new nomenclature scheme for monoclinic amphiboles (Leake et al. 2004) the ideal composition of reference, [sup.A]Na [sup.B](CaMn) [sup.C][[Mg.sub.5][sup.T]([Si.sub.7]Al)[O.sub.22][(OH).sub.2] with Ca > 1 apfu, is an end-member of the newly defined Group 5, and is named parvo-mangano-edenite. Re-examination of the original rock specimen showed significant inter- and intra-crystalline compositional variations, which can be expressed by the [sup.A][Na.sub.-1][sup.T][Al.sub.-1][sup.A][[??].sub.1][sup.T] [Si.sup.1] and [sup.B][Mn.sub.2][sup.B][Ca.sub.-2] exchange vectors. The first vector leads to parvo-manganotremolite, ideally [sup.A][??][sup.B] (CaMn)[sup.C][Mg.sub.5][sup.T][Si.sub.8][O.sub.22][(OH).sup.2] with Ca > 1. The second mechanism was never found to reach Mn dominance; however, crystal-chemical analysis does not provide any evidence of structural limits, and thus the magno-calcic counterparts of the Group 5 amphiboles of this work may occur in similar but Mn-richer genetic environments. The presence of Mn at the B site helps to stabilize the charge arrangement of edenite. The parvo-mangano-edenite crystal with composition closest to the end-member, i.e., [sup.A] ([Na.sub.0.74][K.sub.0.02])[sup.B]([Ca.sub.1.27][Mn.sub.0.73])[sup.C] ([Mg.sub.4.51][Mn.sup.2+.sub.0.28][Fe.sup.2+.sub.0.05][Fe.sup.3+.sub.0.03] [Al.sub.0.12][Ti.sub.0.01])[sup.T]([Si.sub.7.07][Al.sub.0.93] [O.sub.22][(OH).sub.2], has a = 9.8260(5), b = 18.0487(9), c = 5.2840(4) [Angstrom], [beta] = 104.55(1)[degrees], V = 907.1 [Angstrom] (Z = 2); the calculated density is 3.11 g/[cm.sup.3]. The parvo-mangano tremolite crystal, with composition [sup.A]([Na.sub.0.44][K.sub.0.01])[sup.B]([Ca.sub.1.13] [Mn.sub.0.83][Na.sub.0.04][sup.C]([Mg.sub.4.69][Mn.sup.2+.sub.0.21] [Fe.sup.2+.sub.0.03][Fe.sup.3+.sub.0.01][Al.sub.0.06])[sup.T] ([Si.sub.7.52][Al.sub.0.48])[O.sub.22][(OH).sup.2], has a = 9.7807(5), b = 18.0548(9), c = 5.2928(4)[Angstrom], [beta] = [104.19(1)sup.o] V = 906.1 [[Angstrom].sup.3] 3 (Z = 2); the calculated density is 3.08 g/[cm.sup.3.]The different compositions are virtually indistinguishable under the optical microscope, but can be identified by a measure of their unit-cell parameters. The single-crystal FTIR spectrum of parvo-mangano-edenite in the OH-stretching region shows two main absorptions at 3711 and 3671 [cm.sup.-1], plus shoulders at 3695, 3660, and 3641 [cm.sup.-1], respectively. FTIR spectroscopy indicates extensive short-range-order of cations in these amphiboles. Keywords: Analysis, chemical (mineral), amphiboles, crystal structure, parvo-mangano-edenite, parvo-manganotremolite, IR spectroscopy, new minerals

A systematic crystal-chemical investigation of orthorhombic holmquistites has been done to determine the reasons for their limited compositional variations. Structural constraints to the relative stability of [sup.B]Li amphiboles are also suggested by the occurrence of ferro- and ferri-ferroclinoholmquistites, and the lack of clinoholmquistite. Detailed crystal-chemical analysis shows: (1) a remarkable constancy in composition, both in terms of charge arrangement and of limited homovalent [sup.M1.3]([Mg.sub.-1] [Fe.sup.2+]), [sup.M2]([Al.sub.-1][Fe.sup.3+]), and [sup.03] ([OH.sub.-1]F) exchanges, (2) a remarkable constancy in the unit-cell dimensions, with the [Fe.sup.3+] content at the M2 site being the only factor affecting the b edge; (3) complete ordering of Li at the M4 site, in contrast with the common partitioning between the M4 and M3 sites in clinoamphiboles, which however couples with partial A-site occupancy; (4) complete ordering of trivalent cations at the M2 site; (5) an inverse relationship between the [Fe.sup.2+] and the [Fe.sup.3+] contents, which is interpreted as a way to keep the size of the octahedral strip constant; (6) a strong distortion of the octahedral sites, both in terms of angular variance and quadratic elongation. [sup.A][[].sup.B][Li.sub.2][sup.c]([Mg.sub.3][Al.sub.2)[sup.T] [Si.sub.8][O.sub.22][(OH).sub.2] is the amphibole composition composed of the smallest possible structural moduli. Crystallization in Pnma symmetry, where the two double-chains of tetrahedra can assume different conformations, is probably required by the need to obtain a more suitable [5 + 1 ]-coordination for [sup.B]Li, and to shrink the cation-cation distances. This arrangement does not allow for extensive incorporation of larger homovalent substituents, which are hosted via mechanisms implying distortion of the octahedral sites. During this work, a sample with [Fe.sup.2+] slightly but significantly higher than Mg was characterized, and then recognized as a mineral species by the IMA-CNMMN (2004-030). Holotype ferroholmquistite has a = 18.287 (1), b = 17.680 (1), and c = 5.278 (1) [Angstrom], and V = 1706.6(1) [[Angstrom].sup.3]. Its crystal-chemical formula is [sup.A] [K.sub.0.01][Na.sub.0.01][sup.B]([Li.sub.1.88][Mg.sub.0.08] [Na.sub.0.03][Fe.sup.2+.sub.0.01][sup.C]([Al.sub.1.89] [Fe.sup.2+.sub.1.70][Mg.sub.1.39][Mn.sup.2+.sub.0.02])[sup.T] [Si.sub.8.00][O.sub.22]([OH].sub.1.97][F.sub.0.03]). Ferroholmquistite occurs as elongated black to bluish-violet prismatic crystals; it is biaxial negative, with [alpha] = 1.628, [beta] = 1.646, and [gamma] = 1.651 ([lambda] = 589 nm), [2V.sub.x] (calc.) = 55.1[degrees]. It is weakly pleochroic, with [alpha] = colorless, [beta] = pale violet-blue, and [gamma] = blue to deep violet; the calculated density is 3.145 g/[cm.sup.3]. The holotype specimen belongs to the mineral collection of Renato and Adriana Pagano (Italy), and comes from the Greenbushes pegmatite (Western Australia). The analyzed sample has been deposited at the Museum of the Dipartimento di Scienze della Terra, Universita di Pavia (Italy) under the code 2004-01.

Re-examination of holotype 'clinoholmquistite', ideally [sup.A][??] [sup.B] [Li.sub.2] [sup.C]([Mg.sub.3][Al.sub.2][sup.T][Si.sub.8][O.sub.22] [sup.X] [(OH).sub.2](Ginzburg 1965) from the Tastyg spodumene deposit, Tuva, Siberia, Russia by EMP and SIMS analysis and structure refinement shows that the sample consists of a mixture of two distinct amphibole compositions, tremolite and a new amphibole end-member, fluoro-sodic-pedrizite, ideally [sup.A]Na [sup.B] [Li.sub.2] [sup.C] ([Mg.sub.2][Al.sub.2]Li)] [sup.T][Si.sub.8] [O.sub.22] [sup.X][F.sub.2] (IMA-CNMMN 2004-002). Fluoro-sodic-pedrizite from Tastyg has the following crystal-chemical formula and unit-cell parameters: [sup.A]([Na.sub.0.64][K.sub.0.01])[sup.B] ([Li.sub.1.93][Ca.sub.0.04][Na.sub.0.03])[sup.M1]([Mg.sub1.69] [Fe.sup.2+.sub.0.31] [sup.M2]([Al.sub.1.98][Cr.sub.0.01][Zn.sub.0.01]) [sup.M3]([Li.sub.0.64][Fe.sub.2+.sub.0.21][Mg.sub.0.13][Mn.sub.0.02]) [sup.T1]([Si.sub.3.96][Al.sub.0.04])[sup.T2][Si.sub.4] [O.sub.22] [sup.X] ([F.sub.1.10][OH.sub.0.90]), a = 9.368(8), b = 17.616(10), and c.5.271(4) A, [beta] = 102.38(4)[degrees], V = 849.6 [A.sup.3] Z = 2. The structure has been relined to [R.sub.obs] = 2.3% (I > 3[[sigma].sub.1]) and [R.sub.all] = 3.8%. Refined site-scattering values and site-geometries were used, together with EMP and SIMS results, to obtain site populations. Fluoro-sodic-pedrizite is the first amphibole end-member with dominant [sup.C]Li found in Fe-poor geologic environments. The coexisting tremolite contains only 0.002 wt% [Li.sub.2]O and 0.06 wt% [B.sub.2][O.sub.3], probably ordered at the T1 site. Crystal-chemical arguments, as well as preliminary experimental work, suggest clinohohnquistite is unstable.

Synthetic Na[Na.sub.2][Mg.sub.5][Si.sub.8][O.sub.21][(OH).sub.3] is the first triclinic member of the amphibole group, and has a tripling of the unit cell in the b direction. The space group is C[bar.1] and the triple-b repeat gives Z = 6. The unit-cell parameters are: a = 9,883(2), b = 54.082(9), and c = 5.277(1) [Angstrom], [alpha] = 90.045(4)[degrees], [beta] = 103.068(3)[degrees] [gamma] = 89.960(4)[degrees], and V = 2748(1) [[Angstrom].sup.3]. The crystal structure has been refined to [R.sub.1] = 7.6 and w[R.sub.2] = 16.7% for the 1835 reflections with [F.sub.o] > 4[[sigma].sub.F] and for 4832 supercell reflections in the 2[theta] range 2-25[degrees], respectively. The structure is pseudo-monoclinic, but both the intensity distribution and refined model indicate space group C[bar.1]. Compared with the common C2/m amphibole structure, the two halves of an I-beam unit are no longer mirror-related, and the overall structure can be rationalized in terms of two different types of I-beam occurring in the unit cell. The first (with multiplicity 2) is centrosymmetric, and the second (with multiplicity 4) is non-centrosymmetric. There are also significant displacements of the cations, especially at the M4 sites, from their corresponding locations in the C2/m structure. The correlated displacements of Na atoms at the M4 sites permit incorporation of excess protons in pseudo-tetrahedral cavities between two adjacent chains of tetrahedra belonging to different I-beams. Bond-valence calculations and crystal-chemical analysis suggest that excess protons are bonded to O atoms at the O4 sites, and are hydrogen bonded to O atoms at adjacent O2 sites. The infrared spectrum of the amphibole in the principal OH-stretching region has a triplet of sharp bands at 3740, 3727, and 3711 [cm.sup.-1], which are assigned to the three independent 'normal' O3-H groups in the triclinic structure. There is an additional intense and very broad absorption at 3430 [cm.sup.-1] that is resolved only when adsorbed moisture is removed. This band is assigned to the extra H in the structure. All the details provided by structure refinement and the proposed location of the excess H atoms is in accord with previous HRTEM and [sup.29]Si- and [sup.1]H MAS NMR studies of this amphibole.

Mineralogical and crystal-chemical descriptions are provided for two end-members of the new Group 5 introduced by Leake et al. (2004) in the nomenclature of amphiboles. This new classification scheme recognizes the occurrence of compositions with B-site populations intermediate between (Ca,Na) amphiboles and (Mg,Fe,Mn,Li) amphiboles. Its implications for the classification and nomenclature of Li-rich amphiboles are also discussed in this paper. Holotype ferri-ottoliniite [ideally [sup.A][[??].sup.B](NaLi) [sup.C]([Mg.sub.3][Fe.sup.3+.sub.2]) [Si.sub.8] [O.sub.22] [(OH).sub.2]] has a = 9.535(3), b = 17.876(6), c = 5.294(2) [Angstrom], [beta] = 102.54[degrees](1), V = 880.9 [[Angstrom].sup.3], and unit formula [sup.A]([K.sub.0.07][Na.sub.0.38])[sup.B] ([Na.sub.0.07][Li.sub.1.24][Ca.sub.0.06])[sup.C] ([Mg.sub.1.35][Fe.sup.2+.sub.0 .92][Mn.sup.2+.sub.0.13][Zn.sub.0.31][Fe.sup.3+.sub.1.71] [Al.sub.0.10][Ti.sub.0.06][Li.sub.0.42]) [Si.sub.8] [O.sub.22] ([O[H.sub.1.51][F.sub.0.47]). Holotype ferriwhittakerite [ideally [sup.A]Na [sup.B](NaLi) [sup.C]([Mg.sub.2][Fe.sup.3+.sub.2]Li) [Si.sub.8] [O.sub.22] [(OH).sub.2]] has a = 9.712(9), b = 17.851(23), c = 5.297(2) [Angstrom], [beta] = 103.63[degrees](5), V= 892.5 [[Angstrom].sup.3], and unit formula [sup.A]([K.sub.0.13][Na.sub.0.64]) [sup.B]([Na.sub.1.27][Li.sub.0.62][Ca.sub.0.11]) [sup.C]([Mg.sub.l.47][Fe.sup.2+.sub.0.58][Mn.sup.2+.sub.0.12] [Zn.sub.0.40][Fe.sup.3+.sub1.48][Al.sub.0.10][Ti.sub.0.12] [Li.sub.0.73]) [Si.sub.8] [O.sub.22] (O[H.sub.1.30][F.sub.0.72]). The root names have been chosen to acknowledge the contribution given to crystal-chemical studies of minerals, and particularly of amphiboles, by L. Ottolini (Pavia, Italy) and E.J.W. Whittaker (Oxford, U.K.).

In the present work, we characterize the amphibole Na(NaMg)[Mg.sub.5][Si.sub.8][O.sub.22][(OH).sub.2] synthesized at 0.4 GPa and 750, 800, and 850 [degrees]C, and 0.5 GPa, 900 [degrees]C. Experiments at 800 and 900 [degrees]C yielded crystals suitable for single-crystal data collection. Structure refinement shows that synthetic Na(NaMg)[Mg.sub.5][Si.sub.8][O.sub.22][(OH).sub.2] has P[2.sub.1]/m symmetry at room T. The two non-equivalent tetrahedral double-chains differ in their degree of stretching and kinking. The infrared spectrum of synthetic Na(NaMg)[Mg.sub.5][Si.sub.8][O.sub.22][(OH).sub.2] has two well-defined absorption bands at 3742 and 3715 [cm.sup.-1] which can be assigned to O-H bands associated with the two independent anion sites (O3A and O3B) in the structure. The higher frequency band is assigned to the shorter O3B-H2 bond, and the lower tYequency band is assigned to the longer O3A-H1 bond. The broader shape of the 3743 [cm.sup.-1] band is consistent with a stronger interaction of the H2 atom with [sup.A]Na, which is confirmed by structure refinement. Increasing Tof synthesis causes a progressive departure from the ideal stoichiometry via the A[[cube root of].sub.1][sup.B][Mg.sub.1][sup.A][Na.sub.-1][sup.B][Na.sub.-1] substitution, as confirmed by EMPA, structure refinement, and FFIR spectroscopy.

Ferripedrizite, ideally [sup.A][Na.sup.B][Li.sub.2][sup.C] ([Fe.sup.3+.sub.2][Mg.sub.2]Li)[sup.T][Si.sub.8][O.sub.22] [sup.X][(OH).sub.2], is a new amphibole end-member found in episyenites formed after cordierite-bearing porphyritic granites in the Eastern Pedriza Massif (Central System, Spain). It contains the maximum amount of Li that can be incorporated in the amphibole structure. The name was approved by the IMA-CNMMN together with restriction of the use of the prefix sodic in the pedrizite series to compositions with [sup.B]Na > 0.5 apfu; its use for compositions with [Na.sub.tot] > 0.5 apfu has been maintained in the rest of the Mg-Fe-Mn-Li group. Complete solid solution between ferripedrizite and leakeite [ideally, [sup.A][Na.sup.B][Na.sub.2][sup.C]([Fe.sup.3+.sub.2] [Mg.sub.2]Li)[sup.T][Si.sub.8][O.sub.22][sup.X][(OH).sub.2]] has been found in the Pedriza Massif. According to the present nomenclature rules, this join bridges three different amphibole groups. Samples with [sup.B](Mg + Fe + Mn + Li) [greater than or equal to] 1.0 apfu and 0. 0 [less than or equal to] [sup.B]Na [less than or equal to] 0.50 apfu belong to the Mg-Fe-Mn-Li group and are termed ferripedrizite; samples with [sup.B](Mg + Fe + Mn + Li) [greater than or equal to] 1.0 apfu and 0.50 < [sup.B]Na [less than or equal to] 0.99 apfu belong to the Mg-Fe-Mn-Li group and are called sodicferripedrizite; samples with [sup.B](Mg + Fe + Mn + Li) < 1.0 apfu and [sup.B]Na [greater than or equal to] 1.50 apfu belong to the sodic group and are named leakeite; samples with [sup.B] (Mg + Fe + Mn + Li) < 1.0 apfu and 1.0 [less than or equal to] [sup.B]Na < 1.50 apfu belong to the sodic-calcic group (albeit Ca is negligible) and deserve a new root name. The ferripedrizite sample from Pedriza is black, vitreous, translucent, non-fluorescent, and brittle, and has gray streak, H = 6, uneven fracture, perfect {110} cleavage, [D.sub.means] = 3.15, [D.sub.calc] = 3.19 g/[cm.sup.3]. It is strongly pleochroic, X = yellow green, Y = green blue, Z = bluish green (Y = Z [much greater than] X), Z = b, Y ^ c = 15(6)[degrees], X ^ a = 3[degrees]. It is biaxial positive: [alpha] = 1.695(1), [beta] = 1.700(2), and [gamma] = 1.702(1); [2V.sub.z] = 125(17)[degrees], dispersion r > v. It is monoclinic, space group C2/m, a = 9.501(1), b = 17.866(2), c = 5.292(1) [Angstrom], [beta] = 102.17(2)[degrees], V = 878.1(2) [[Angstrom].sup.3]. The ten strongest lines in the X-ray powder-diffraction pattern [d in [Angstrom],(I),(hkl)] are: 8.251(3)(110), 4.466(2)(040), 3.411(2)(131), 3.050(10)(310), 2.747(3)(330), 2.711 (4)(151), 2.495 (2)(202), 2.161 (2)(261), 1.642(4)(461), 1.394(3)(661). Structure refinement and electron- and ion-microprobe analysis of a crystal with composition [sup.A]([K.sub.0.04] [Na.sub.0.52])[sup.B]([Na.sub.0.25][Ca.sub.0.05][Li.sub.1.70])[sup.C] ([Li.sub.0.64][Fe.sup.3+.sub.1.64][Mg.sub.1.49][Fe.sup.2+.sub.0.85] [Al.sub.0.21][Ti.sub.0.09] [Mn.sub.0.07][Zn.sub.0.01]) [sup.T][Si.sub.8][O.sub.22] [sup.X](O[H.sub.1.31][F.sub.0.69]) are provided, together with some discussion on cation ordering.

Detailed X-ray single-crystal structure refinements and complete (SIMS + EMPA) microprobe chemical analyses of a series of non-metamict samples of hellandite recently found in Latium (Italy), together with a critical re-evaluation of the existing data on hellandite, allow a better understanding of the crystal-chemistry of the hellandite group. Relative to the crystal structure determined by Mellini and Merlino (1977) for a Y-rich sample from Predazzo (Italy), a new tetrahedrally coordinated site has been detected; this may be fully, or in part, occupied by Li and Be. These cations occur at the center of the tetrahedral cavity where the H atom, which is bonded to the O5 O atom, protrudes; thus the H content in hellandite is constrained to values [less than or equal to] 2 - (Li + Be + F). A new general formula for hellandite-group minerals is proposed: [X.sub.4][Y.sub.2]Z[T.sub.2][[B.sub.4][Si.sub.4][O.sub.22]][W.sub.2], where X = Na, Ca, Y, LRE[E.sup.3+] at the eightfold-coordinated M3 and M4 sites; Y = Ca, Y, HRE[E.sup.3+], [Th.sup.4+ at the eightfold-coordinated M2 site; Z = Al, [Mn.sup.3+], [Fe.sup.3+], [Ti.sup.4+] at the octahedral M1 site; T = [square] (vacancy), Li, Be at the new tetrahedrally coordinated site; and W = OH, F, [O.sup.2-] at the 05 site. Eight root end-member compositions were identified; four of these correspond to known compositions: hellandite-(REE), tadzhikite-(REE), and two new minerals, mottanaite-(Ce) and ciprianiite, which are described in a companion paper (Della Ventura et al. 2002). The root-name tadzhikite must be used for samples with [Ti.sup.4+] > 0.5 apfu, with no reference to the OH content. Hellandite is an REE mineral. Rare-earth elements occur at two distinct sites (M2 and M4), with a strong preference for M2 (particularly HREE). Thus, one or two Levinson modifiers can be added to the root name to correctly describe the species. A sequence of incorporation based on crystalchemical arguments is provided and allows evaluation of the site populations for nomenclature purposes. This redefinition of the hellandite group and the new nomenclature rules have been approved by the IMA Commission on New Minerals and Mineral names (code 00-F).

Two new minerals of the hellandite group were found within alkali-syenitic ejecta enclosed in pyroclastic formations of the Roman Comagmatic Province (Latium, Italy). Mottanaite-(Ce) [ideally [sup.X][Ca.sup.Y.sub.4][(CeCa).sup.Z][Al.sup.T][Be.sub.2] [([Si.sub.4][B.sub.4][O.sub.22]).sup.W][O.sub.2]] and ciprianiite [ideally [sup.X][Ca.sup.Y.sub.4][[(Th,U)(REE)].sup.Z][Al.sup.T][[square].sub.2] ([Si.sub.4][B.sub.4][O.sub.22]) [sup.W][(OH, F).sub.2]] occur as transparent, brown-colored, tabular euhedral crystals in miarolitic cavities and voids of the ejecta, which consist mainly of sanidine and plagioclase (An ranging from 20 to 80%), with minor amounts of feldspathoid, clinopyroxene and/or clinoamphibole, magnetite, titanite, and zircon. Locally, accessory minerals include britholite-(Ce), baddeleyite, phosphate to silico-phosphate phases close in composition to the brabantite-cheralite series, thorite, fluorite, danburite, and vonsenite. The genesis of the new hellandite end-members can be related to late-stage post magmatic hydrothermal fluids enriched in Zr, Ti, REEs, and actinide elements. Both mottanaite-(Ce) and ciprianiite have a vitreous luster and are non-fluorescent. Cleavage is absent in mottanaite-(Ce), fair to good in ciprianiite, {100}. Twinning is frequently observed in ciprianiite. Due to the strong intra-crystalline chemical zoning and twinning, physical properties could be measured only for mottanaite-(Ce). [D.sub.meas] is 3.61(4) g/[cm.sup.3], [D.sub.calc] is 3.88 g/[cm.sup.3]. Mottanaite-(Ce) is biaxial negative, with [alpha] = 1.680(5), [beta] = 1.694(2), [gamma] = 1.708(5); 2[V.sub.meas] ~90 [degrees]. Both minerals are monoclinic, space group P2/a, Z = 2. Unit-cell parameters for the crystals studied are: a = 19.032(9) [Angstrom], b = 4.746(3) [Angstrom], c = 10.248(5) [Angstrom], [beta] = 110.97(5) [degrees], V = 864.3(8) [[Angstrom].sup.3] for mottanaite-(Ce), and a = 19.059(5) [Angstrom], b = 4.729(1) [Angstrom], c = 10.291(4) [Angstrom], [beta] = 111.33(2) [degrees], V = 864.0(5) [[Angstrom].sup.3] for ciprianiite. Single-crystal structure refinement confirmed the presence of a further distorted tetrahedral site which was first detected in a hellandite-(Ce) sample from Latium (Oberti et al. 1999). This site is occupied by Be ([+ or -] Li) in stoichiometric mottanaite-(REE), whereas it mainly hosts hydrogen (bonded to the 05 oxygen atom) in ciprianiite and hellandite-(REE); solid solution between the end-members is possible, as shown by the studied samples. The chemical composition of the refined crystals was obtained by combining EMPA (for medium-Z elements) and SIMS analyses (for low- and high-Z elements); their results are in excellent agreement with the chemical information obtained from the structure refinements. The crystal-chemical formulae of the crystals studied, recalculated on the basis of 24 anions, are [sup.M3,4][Ca.sup.M2.sub.4] [[RE[E.sub.1.45][Ca.sub.0.37][(Th,U).sup.4+.sub.0.17] [Y.sub.0.01]].sub.[SIGMA]=2][sup.M1][([Al.sub.0.50] [Fe.sup.3+.sub.038][Mg.sub.0.03] [Ti.sup.4+.sub.0.07]).sub.[SIGMA]=0.99][sup.T] ([Be.sub.1.18][Li.sub.0.02][[square].sub.0.37]) [B.sub.3.99][Si.sub.3.98][O.sub.22][sup.O5][([O.sup.2-.sub.1.04] [F.sub.0.53]O[H.sub.0.43]).sub.[SIGMA]=2] for mottanaite-(Ce); and [sup.M3,4][Ca.sub.4][sup.M2][[RE[E.sup.3+.sub.0.72] [(Th,U).sup.4+.sub.0.66][Ca.sub.0.60][Y.sub.0.02]].sub.[SIGMA]=2] [sup.M1][([Al.sub.0.48][Fe.sup.3+.sub.0.38][Ti.sup.4+.sub.0.10][Mg.sub.0.05] [Mn.sup.3+.sub.0.02]).sub.[SIGMA]=1.03][sup.T] ([Be.sub.0.82][[square].sub.0.60][Li.sub.0.04]) [B.sub.4.00][Si.sub.4.00][O.sub.22][sup.O5][([O.sup.2-.sub.0.97]O [H.sub.0.54][F.sub.0.49]).sub.[SIGMA]=2] for ciprianiite.

Fluoro-edenite, ideally Na[Ca.sub.2][Mg.sub.5]([Si.sub.7]Al)[O.sub.22][F.sub.2] was found both as prismatic or acicular crystals of millimetric size and as fibers in the rock cavities in gray-red altered benmoreitic lavas occurring at Biancavilla (Etnean Volcanic Complex, Catania, Italy). It is associated with feldspars, quartz, clino- and orthopyroxene, fluoro-apatite, ilmenite, and hematite, and probably crystallized from late-stage hydrothermal fluids. Fluoro-edenite is transparent, intense yellow, non-fluorescent, has vitreous to resinous luster, and gives a yellow streak parallel to the c axis; Mohs' hardness 5-6, [D.sub.calc] = 3.09 g/[cm.sup.3], perfect cleavage on {110}, and conchoidal fracture. In plane-polarized light, fluoro-edenite is birefringent (1st order), biaxial negative, [alpha] = 1.6058(5), [beta] = 1.6170(5), [gamma] = 1.6245(5), 2[V.sub.calc] = 78.09 [degrees] , Y [equivalent to] [beta] [perpendicular to] (010), and [gamma]:Z = 26 [degrees] . No pleochroism is observed. Fluoro-edenite is monoclinic, space group C2/m, a = 9.847(2)[Angstrom], b = 18.017(3) [Angstrom], c = 5.268(2) [Angstrom], [beta] = 104.84(2) [degrees] , V = 903.45 [[Angstrom].sup.3], Z = 2; the ten strongest X-ray diffraction lines in the powder pattern are [d(I, hkl)]: 3.125(10, 310), 8.403(6,110), 3.271(5,240), 2.807(4,330), 2.703(3,151), 1.894(2,510), 2.938(2,221), 1.649(2,461), 3.376(2,131), 1.438(2,661). IR analysis showed absorption bands at 1066, 991,791,738,667,517,475 [cm.sup.-1], and no bands in the OH-stretching region. Structure refinement allowed determination of cation site-preference and ordering. Microprobe analysis of the refined crystal gave Si[O.sub.2] 52.92, Ti[O.sub.2]0.29, [Al.sub.2][O.sub.3] 3.53, Fe[O.sub.t] 2.50, MnO 0.46, MgO 22.65, CaO 10.83, [Na.sub.2]0 3.20, [K.sub.2]O 0.84, F 4.35, Cl 0.07 wt%, and the crystal-chemical formula obtained by combining all the available data is: [sup.A]([Na.sub.0.56][K.sub.0.15]) [sup.B]([Na.sub.0.30][Ca.sub.1*62] [Mg.sub.0.03][Mn.sub.0.05]) [sup.C]([Mg.sub.4.68][Fe.sup.2+.sub.0.19] [Fe.sup.3+.sub.0.10][Ti.sup.4+.sub.0.03]) [.sup.T]([Si.sub.7.42][Al.sub.0.58]) [O.sub.22] [.sup.03][([F.sub.1.98] [Cl.sub.0.02]).sub.2].

A procedure was developed for accurate quantification of REE, actinides, and light elements in complex matrixes of interest in earth and material sciences (hellandite and britholite, the REE analogue of apatite). These minerals show a peculiar chemical composition due to the coexistence of high amounts of LREE, U, Th with variable quantities of H, Li, Be, B, and F. Molecular interferences were resolved, and problems arising from unpredictable matrix effects and lack of reference materials were overcome. X-ray single-crystal structure refinement (SREF), which is not affected by matrix effects and does not require analytical standardization, was used to precisely estimate (by means of both site-scattering value and site geometry) in a wholly independent way the amounts and the distribution of the various groups of elements. The combined SIMS-SREF approach allowed us to obtain results of impact for mineralogy and also allowed the accuracy of SIMS investigation to be fixed. The capabilities of SIMS in the quantification of light (Z 57) elements as both minor and major constituents ((mathematical expression not reproducible in ASCII)REE(sub ox)) up to approximately 70 wt % in britholite) are shown. This approach may open new perspectives for the in situ analysis of chemically complex materials.

The crystal structure of a Th-U-rich, Y-poor hellandite-(Ce) occurring in a volcanic ejectum from Capranica (Vico volcanic complex, Latium, Italy) was refined to an R index of 1.5% for 2226 observed reflections [I > 3 [Sigma](I)]. Hellandite from Capranica is monoclinic P2/a with a = 19.068 (8), b = 4.745 (2), c = 10.289 (3) [Angstrom], [Beta] = 111.18 (3)[degrees]. The extra-framework (distorted) tetrahedral cavity, usually occupied by H in hellandite, is partially (35-40%) occupied by Be and/or Li. When this is the case, the [[B.sub.4][Si.sub.4][O.sub.22]] tetrahedral chains of hellandite are locally cross-linked to form a sheet, which is built up by the same types of rings as in semenovite but in a different arrangement. The structure refinement and the electron- and ion-microprobe analyses provide constraints on hellandite-group crystal chemistry. The presence of (4)(Be, Li) at the Be site is coupled with the substitution of F and/or O for OH at the O5 site; the amount of extra-framework cations thus constrains the OH content in the general formula. X-ray data exclude the presence of other OH sites in the structure, in agreement with direct H determination by ion probe (1.02 H apfu + 0.98 F apfu = 2.0 apfu of monovalent anions at 05 vs. 4.5-8 apfu proposed previously). The complete chemical analysis also eliminates the need for a vacancy at the REE sites. The general formula of hellandite-group minerals is thus[(Ca,REE).sub.8] (Th,U,Y,REE).sub.4][ Ti,[Fe.sup.3+],Al).s b.2][(O,F,O[H.sub.x]).sub.4][(Be,Li).sub.4-x][Si.sub.8][B.sub.8][O.sub.44], where electroneutrality is assured by the appropriate mixing of heterovalent substituents at the M sites.

Ferro-papikeite, ideally NaFe22+(Fe32+Al2)(Si5Al3)O22(OH)2, is a new mineral of the amphibole supergroup from the Filipstad Municipality, Värmland County, Central Sweden, where it occurs in a medium-grade felsic metavolcanic rock. Ferro-papikeite is pale brown with a translucent luster, has a colorless to very pale-brown streak, and shows no fluorescence under long-wave or short-wave ultraviolet light. Grains are subhedral, 0.4–3.0 mm in size, and show well-developed {210} cleavage. It has a Mohs hardness of ~6 and is brittle with a splintery fracture, has the characteristic perfect {210} cleavage of orthorhombic amphiboles, intersecting at ~56°, and the calculated density is 3.488 g/cm3. In transmitted plane-polarized light, ferro-papikeite is moderately pleochroic X = very pale brown, Y = Z = honey brown; X < Y = Z. Ferro-papikeite is biaxial (+), α = 1.674(2), β = 1.692(2), γ = 1.716(2), 2Vmeas = 86.2(9) and 2Vcalc = 88.3°, dispersion is r < v, weak. The orientation is: X || a, Y || b, Z || c. Ferro-papikeite is orthorhombic, space group Pnma, a = 18.628(4), b = 17.888(4), c = 5.3035(11) Å, V = 1767.2(6) Å3, Z = 4. The strongest ten X‑ray diffraction lines in the powder pattern are [d in Å(I) (hkl)]: 8.255(100)(210), 3.223(39)(440), 3.057(68)(610), 2.824(28)(251), 2.674(41)(351), 2.572(56) (161,621), 2.549(38)(202), 2.501(50)(261,451), 2.158(25)(502), and 1.991(31)(661). Chemical analysis by electron microprobe gave SiO2 36.50, Al2O3 22.24, TiO2 0.09, FeO 31.54, MnO 0.65, MgO 5.48, CaO 0.08, Na2O 2.35, F 0.22, H2Ocalc 1.85, O=F –0.09, sum 100.91 wt%. The formula unit, calculated on the basis of 24 (O+OH+F) with (OH) = 2 apfu and Fe3+ = 0.13 apfu (determined from the distance) is A(Na0.70Ca0.01)B+C(Mg1.25Fe23.90+ Mn20.08+ Al1.62Fe30.13+ Ti40.01+)Σ6.99T(Si5.60Al2.40)Σ8O22(OH1.89F0.11)2. The crystal structure of ferro-papikeite was refined to an R-index of 3.60% using 2335 unique observed reflections collected with MoKa X-radiation. [4]Al3+ is ordered over the four T sites as follows: T 1B > T1A > T2B >> T2a, [6]Al3+ is completely ordered at M2, and Fe2+ is strongly ordered at M4. The A site is split with Na+ strongly ordered at A1. End-member ferro-papikeite is related to end-member gedrite, □Mg2(Mg3Al2)(Si6Al2)O22(OH)2, by the substitutions Na+ → □, Fe2+ → Mg, and Al3+ → Si4+. The description of ferro-papikeite as a new species further emphasizes the compositional similarities between the monoclinic calcium amphiboles and the orthorhombic magnesium-iron-manganese amphiboles. [ABSTRACT FROM AUTHOR]

Electron microprobe analysis of amphiboles from Pargas, Finland, shows up to 2.42 Ca apfu (atoms per formula unit), far in excess of the usual maximum value of 2.00 Ca apfu observed in amphiboles. The most Ca-rich composition is [Mathematical Expression Omitted]. Fluor-cannilloite, ideally Ca[Ca.sub.2]([Mg.sub.4]Al)([Si.sub.5][Al.sub.3])[O.sub.22][F.sub. 2], is a new amphibole species in which Ca is dominant at the A site. Fluor-cannilloite occurs as isolated anhedral grains and small granular aggregates in a marble together with calcite, muscovite, anorthite, aluminous diopside, pyrope, and fluorite. It is grayish green with a grayish white streak, brittle, H = 6, [D.sub.meas] = 3.05 g/[cm.sup.3], and shows perfect {110} cleavage. In plane-polarized light, it is pale greenish gray to almost colorless, rather cloudy and mottled in appearance, and is not pleochroic. Fluor-cannilloite is biaxial positive, [Alpha] = 1.611(2), [Beta] = 1.616(2), [Gamma] = 1.633(2), 2V = 49(2) [degrees], dispersion weak r > v. It is monoclinic, space group C2/m, a = 9.826(4), b = 17.906(9), c = 5.301(3) [angstrom], [Beta] = 105.41(4) [degrees], V = 899.2 [[angstrom].sup.3], Z = 2. The ten strongest X-ray diffraction lines in the powder pattern [d in [angstrom](I)(hkl)] are 8.936(4)(020), 8.355(3)(110), 3.366(4)(131), 3.107(7)(310), 2.686(10)(151), 2.578(10)(061), [Mathematical Expression Omitted], 2.165(6)(171), 2.036(5)(202), [Mathematical Expression Omitted]. The structures of fluor-cannilloite and another Ca-rich amphibole from Madagascar were refined to R indices of [approximately] 1.5% using reflection intensities collected with MoK[Alpha] X radiation. Site populations were assigned from the refined site-scattering values, considerations of mean bond lengths, and the unit formulas calculated from the electron micro-probe analyses. Both the electron microprobe data and the site-scattering refinements show significant Ca (up to 0.52 apfu) together with Na and K at the A site. Both A2 and Am sites are occupied, with the A2 site having the higher electron density. Local bond-valence considerations indicate that Ca is equally partitioned between the A2 and Am sites, whereas K occupies Am and Na occupies A2.

Analysis of ungarettiite, a new anhydrous amphibole from the Hoskins mine Grenfell, New South Wales, Australia, by electron microprobe reveals the composition of ungarettiite as Na,Na2(Mn(sub 2)(super 2+)(Mn(sub 3)(super 3+))Si8O22O2. X-ray crystallography of the sample reveals that majority of M1, M2 and M3 sites are occupied by Mn. Bond valence analysis reveals that a divalent anion O2- occupies the O3 site and this is consistent with the electroneutrality of the structural formula.

Site scattering refinement and ion microprobe analysis reveal that Li is predominant is monoclinic alkali amphiboles having discrete amphibole structures with few chain-width disorders in microstructure and containing manganese oxide, included during rapid growth of the amphibole. Li-bearing alkali amphiboles are identified by the low X-ray scattering at the M3 site. All the transition metals are confined to M1 and M2 sites bearing Mg as the other cation at M3, making it possible to derive Li and Mg by site-scattering refinement.

Analyses to establish the structure of preiswerkite, Na(Mg2Al)(Si2Al2)O10(OH)2, from the type locality at Geisspfad, Switzerland, revealed that micas with extremely different compositions have some similar structural characteristics. Single-crystal X-ray diffraction and refinement were used in the analysis. The 1M polytype has a space group C2/m.