The crystal structures of green (brown) variants of manitobaite, ideally (Na 16 □)Mn 2+ 25 Al 8 (PO 4 ) 30 , monoclinic, Pc , Z = 2: green: a 13.4517(7), b 12.5266(7), c 26.6765(13) A, β 101.582(1)°, V 4403.6(7) A 3 , D calc. 3.642 g/cm 3 ; brown: 13.4499(6), b 12.5046(5), c 26.6148(11) A, β 101.221(1)°, V 4390.7(5)(3) A 3 , D calc. 3.621 g/cm 3 , from pegmatite #22 at Cross Lake, Manitoba, Canada, have been solved by direct methods and refined to R 1 = 5.0 (6.0)% for 22,580 (25,613) unique ( F o > 4σ F ) reflections collected on a Bruker single-crystal P 4 diffractometer equipped with a 4K CCD detector and Mo K α X-radiation. Chemical analysis by electron microprobe plus Fe 3+ determination by Mossbauer spectroscopy gave: green: P 2 O 5 44.19, Al 2 O 3 6.91, Fe 2 O 3 1.73, FeO 6.23, MnO 27.57, ZnO 0.54, MgO 0.73, CaO 1.71, Na 2 O 9.97, sum 99.58 wt%; brown: P 2 O 5 44.42, Al 2 O 3 6.96, Fe 2 O 3 3.54, FeO 4.66, MnO 27.86, ZnO 0.53, MgO 0.81, CaO 1.59, Na 2 O 8.94, sum 99.32 wt%. The resulting empirical formulae are as follows: green: Na 15.55 Ca 1.47 Mg 0.88 Fe 2+ 4.19 Mn 2+ 18.78 Zn 0.32 Al 6.54 Fe 3+ 1.05 P 30.08 O 120 ; brown: Na 13.90 Ca 1.37 Mg 0.97 Fe 2+ 3.12 Mn 2+ 18.92 Zn 0.31 Al 6.58 Fe 3+ 2.09 P 30.15 O 120 . The general formula of manitobaite is (Na 16 □)(Mn 2+ ,Fe 2+ ,Mg,Zn,Ca) 25 (Al,Fe 3+ ) 8 (PO 4 ) 30 , and the end-member formula is (Na 16 □)Mn 2+ 25 Al 8 (PO 4 ) 30 . There are 80 cation sites and 120 anion sites in the structure. There are 30 tetrahedrally coordinated sites occupied by P, 33 octahedrally coordinated sites occupied by Mn 2+ , Fe 2+ , Al, Fe 3+ plus minor Mg and Zn, and 17 sites occupied predominantly by Na with coordination numbers from [5] to [8]. Manitobaite is an ordered superstructure of the alluaudite structure. In particular, there are eight octahedrally coordinated sites occupied predominantly by Al, emphasizing the key role of Al in producing superstructures in these minerals.

The crystal chemistry of tapiolite is more complicated than previously recognized. Perusal and synthesis of relatively recent publications reveals a 'hidden' story about tapiolite, one that: (1) permits quantification of the effects of Mn, Fe(3+), Ti (and Sn) upon the unit-cell parameters of maximally ordered tapiolite; (2) shows that the effect of Nb = Ta substitution upon unit-cell parameters is insignificant; (3) casts doubt on the usefulness of heating experiments for accurately evaluating cation order in tapiolite; (4) suggests that rutile exsolves from tapiolite upon heating in air at lower temperatures than previously established; (5) shows that the maximum solubility of TiO(2) in FeTa(2)O(6) tapiolite during the later stages of crystallization of granitic pegmatites is similar to 1 mol.%; (6) shows that the heating paths for at least some natural tapiolite samples are not necessarily linear, consisting of two sequential steps; (7) sheds doubt on the usefulness of unit-cell parameters as quantitative measures of long-range cation order, Q, in tapiolite; but (8) does show that the intensity ratio I(011)/I(110) can provide an accurate and reasonably precise measure of cation order in tapiolite.

Manitobaite, ideally Na 16 Mn 2+ 25 Al 8 (PO 4 ) 30 , is a new mineral species from Cross Lake, Manitoba, Canada. It occurs as large crystals or cleavage masses intergrown with other phosphate minerals in a phosphate pod in the intermediate and core zones of pegmatite #22 on the southeastern shoreline of a small unnamed island in Cross Lake, Manitoba, about 5 km north–northwest of the Cross Lake settlement, longitude 54° 41′ N, latitude 97° 49′ W. Associated minerals are fluorapatite, chlorapatite, bobfergusonite, eosphorite, dickinsonite, fillowite, triploidite, goyazite, perloffite, beusite, triplite, as well as quartz, K-feldspar, muscovite, schorl, beryl, spessartine, gahnite and (Nb,Ta,Sn) oxides. Manitobaite is opaque in large crystals (up to 4 cm), and transparent to translucent in small ( −3 , respectively. Manitobaite is biaxial negative with α 1.682, β 1.691, γ 1.697 (all ±0.001), with X ∧ a = 31.7° (in β obtuse), Y || b , Z ∧ c = 20.2° (in β acute); 2 V obs = 78.1(6)°, 2 V calc = 77.9°. It is pleochroic X = orange brown, Y = green, Z = greenish brown, with absorption Y ≥ Z > X and dispersion r > v , medium. Manitobaite is monoclinic, Pc , a 13.4516(15), b 12.5153(16), c 26.661(3) A, β 101.579(10)°, V 4397.1(6) A 3 , Z = 2, a:b:c = 1.07482:1:2.13027. The strongest seven lines in the X-ray powder-diffraction pattern [ d in A( I )( hkl )] are: 2.715(100)(242), 2.730(50)(404), 3.494(47)(313), 3.078(27)(317), 2.518(22)( 515), 2.881(21)(119), and 6.260(20)(020). A chemical analysis with an electron microprobe gave P 2 O 5 44.19, Al 2 O 3 6.91, FeO 7.79, MnO 27.57, ZnO 0.54, MgO 0.73, CaO 1.71, Na 2 O 9.97, for a total of 99.58 wt%. The resulting empirical formula, using the valence states of Fe determined by Mossbauer spectroscopy, is Na 15.55 Ca 1.47 Mg 0.88 Fe 2+ 4.19 Mn 2+ 18.78 Zn 0.32 Al 6.54 Fe 3+ 1.05 P 30.08 O 120 based on 120 O 2− anions pfu . The general formula is ( Na ,Ca,□) 16 ( Mn 2+ ,Fe 2+ ,Ca,Al,Fe 3+ ,Mg,Zn) 25 ( Al ,Fe 3+ ,Mg,Mn 2+ , Fe 2+ ) 8 (PO 4 ) 30 , and the end-member formula is Na 16 Mn 2+ 25 Al 8 (PO 4 ) 30 . The crystal structure of manitobaite is an ordered superstructure of the alluaudite arrangement with a cell volume five times that of alluaudite.

Abstract Holtite, approximately (Al,Ta,□)Al6(BO3)(Si,Sb3+,As3+)Σ3O12(O,OH,□)Σ3, is a member of the dumortierite group that has been found in pegmatite, or alluvial deposits derived from pegmatite, at three localities: Greenbushes, Western Australia; Voron'i Tundry, Kola Peninsula, Russia; and Szklary, Lower Silesia, Poland. Holtite can contain >30 wt.% Sb2O3, As2O3, Ta2O5, Nb2O5, and TiO2 (taken together), but none of these constituents is dominant at a crystallographic site, which raises the question whether this mineral is distinct from dumortierite. The crystal structures of four samples from the three localities have been refined to R1 = 0.02-0.05. The results show dominantly: Al, Ta, and vacancies at the Al(1) position; Al and vacancies at the Al(2), (3) and (4) sites; Si and vacancies at the Si positions; and Sb, As and vacancies at the Sb sites for both Sb-poor (holtite I) and Sb-rich (holtite II) specimens. Although charge-balance calculations based on our single-crystal structure refinements suggest that essentially no water is present, Fourier transform infrared spectra confirm that some OH is present in the three samples that could be measured. By analogy with dumortierite, the largest peak at 3505-3490 cm-1 is identified with OH at the O(2) and O(7) positions. The single-crystal X-ray refinements and FTIR results suggest the following general formula for holtite: Al7-[5x+y+z]/3(Ta,Nb)x□[2x+y+z]/3BSi3-y(Sb,As)yO18-y-z(OH)z, where x is the total number of pentavalent cations, y is the total amount of Sb + As, and z ≤ y is the total amount of OH. Comparison with the electron microprobe compositions suggests the following approximate general formulae Al5.83(Ta,Nb)0.50□0.67BSi2.50(Sb,As)0.50O17.00(OH)0.50 and Al5.92(Ta,Nb)0.25□0.83BSi2.00(Sb,As)1.00O16.00(OH)1.00 for holtite I and holtite II respectively. However, the crystal structure refinements do not indicate a fundamental difference in cation ordering that might serve as a criterion for recognizing the two holtites as distinct species, and anion compositions are also not sufficiently different. Moreover, available analyses suggest the possibility of a continuum in the Si/(Sb + As) ratio between holtite I and dumortierite, and at least a partial continuum between holtite I and holtite II. We recommend that use of the terms holtite I and holtite II be discontinued.

The (YREE,U,Th)-(Nb,Ta,Ti) oxide minerals in REE-enriched granitic pegmatite and A- and I-type granites are primarily comprised of the fergusonite, samarskite, euxenite, aeschynite and pyrochlore groups. They are typically metamict and altered. and can be difficult to identify on a structural basis (XRD); consequently, examination of sample composition may be the most reliable approach to their identification. Canonical discriminant analysis can be used to discriminate among the various groups, and to assess the style and degree of alteration affecting samples. Identification of individual species should be made on the basis of previously published guidelines or, in their absence, on the basis of the "50% rule" of the IMA. Vector analysis shows that alteration typically pushes the compositions of samarskite, euxenite- and aeschynite-group minerals in a direction that causes them to resemble pyrochlore-group minerals. For this reason, it has been historically difficult to determine the exact nature of "viethofingite", "hjelmite" and "amparigabeite"; all are shown to be altered varieties of samarskite-group minerals. Yttrotantalite-(Y) is shown to be a member of the samarskite group, not the fergusonite group.

The classification of granitic pegmatites was frequently attempted during the past century, with variable degrees of success and applicability. Internal structure, paragenetic relationships, bulk chemical composition, petrogenetic aspects, nature of parent medium, and geochemical features were applied. However, all schemes were marked by contemporary degrees of understanding of these parameters, and most attempts were hindered by ignoring differences in geological environment. Substantial progress was achieved only since the late 1970s. The classification is approached here from two directions, based on but broadened and refined from earlier works by Ginsburg and Cerný. The first concept deals with geological location, leading to division of granitic pegmatites into five classes (abyssal, muscovite, muscovite – rare-element, rare-element, and miarolitic), most of which are subdivided into subclasses with fundamentally different geochemical (and in part geological) characteristics. Further subdivision of most subclasses into types and subtypes follows more subtle differences in geochemical signatures or P–T conditions of solidification, expressed in variable assemblages of accessory minerals. The second approach is petrogenetic, developed for pegmatites derived by igneous differentiation from plutonic parents. Three families are distinguished: an NYF family with progressive accumulation of Nb, Y and F (besides Be, REE, Sc, Ti, Zr, Th and U), fractionated from subaluminous to metaluminous A- and I-type granites that can be generated by a variety of processes involving depleted crust or mantle contributions; a peraluminous LCT family marked by prominent accumulation of Li, Cs and Ta (besides Rb, Be, Sn, B, P and F), derived mainly from S-type granites, less commonly from I-type granites, and a mixed NYF + LCT family of diverse origins, such as contamination of NYF plutons by digestion of undepleted supracrustal rocks.

La manganokukisvumite, de formule ideale Na 6 MnTi 4 Si 8 O 2 8 .4H 2 O, est une nouvelle espece minerale decouverte a la carriere Poudrette, au mont Saint-Hilaire, comte de Rouville, Quebec (IMA 2002-029). On la trouve dans de petites vacuoles d'une breche syenitique riche en albite; lui sont associes aegyrine, microcline, albite, annite, chalcopyrite, pyrite, pyrrhotite, natrolite, labuntsovite-Mn, titanite, calcite, un membre du groupe de la chlorite, magnetite, fluorapatite, elpidite et sodalite. Les cristaux de manganokukisvumite sont incolores a transparents avec un eclat vitreux et une rayure blanche. Elle est non-fluorescente en lumiere ultra-violette (ondes courtes ou longues). Les cristaux sont extremement minces, aplatis et en forme d'epee, jusqu'a 0.5 mm en longueur, et generalement en regroupes en rosette. Les formes observees sont les pinacoides {100} et {010} et un prisme que nous etions incapables de mesurer. Il ne semble pas y avoir de macle. La durete est entre 5½ et 6. Le mineral est sectile, legerement flexible, sans clivage apparent, mais avec une fracture en echapes. La manganokukisvumite est biaxe negative, avec α(calc.) 1.657, β 1.744 ′ 0.003 et γ 1.792 ′ 0.003 (pour λ = 589 nm); 2V m e s 70° (methode de Kamb). Il n'y a aucune dispersion et aucun pleochroisme: l'orientation optique estX = a, Y = b et Z = c. Il s'agit d'un mineral orthorhombique, groupe spatial Pccn, ayant les parametres reticulaires suivants, affines a partir des donnees sur poudre: a 29.05(2), b 8.612(6), c 5.220(4) A, V 1305.9(3) A 3 et Z = 2. Les raies les plus intenses du spectre de diffraction, methode des poudres [d en A(D(hkl)] sont: 14.47(100)(200), 6.43(20)(310), 4.83(10)(600), 3.743(10)(710), 3.025(40)(910), 2.881 (20)(521 ), 2.591(10)(721), 2.458(10(402) et 2.146(10)(930). Une analyse obtenue avec une microsonde electronique, complementee avec un spectre d'absorption infra-rouge, a donne Na 2 O 15.61, K 2 O 0.21, MgO 0.26, CaO 0.08, MnO 5.48, FeO 0.57, Al 2 O 3 0.16, Ce 2 O 3 0.18, SiO 2 41.74. TiO 2 26.90, Nb 2 O 5 0.68, H 2 O 6.25 (quantite calculee par stoechiometrie), pour un total de 98.12% (poids). La formule empirique, calculee sur une base de 32 atomes d'oxygene, est: (Na 5 . 8 1 K 0 . 0 5 Ca 0 . 0 2 Ce 0 . 0 1 ) Σ 5 . 8 9 (Mn 0 . 8 9 Fe 0 . 0 9 Mg 0 . 0 7 Al 0 . 0 4 ) Σ 1 . 0 9 (Ti 3 . 8 8 Nb 0 . 0 6 ) Σ 3 . 9 4 Si 8 . 0 1 O 2 8 .4H 2 O ou, en termes plus simples, Na 6 MnTi 4 Si 8 O 2 8 .4H 2 O. La densite calculee (a partir de la formule empirique) est 2.88 g/cm 3 , et la densite mesuree est 2.86(1) g/cm 3 . L'indice de compatibilite selon la loi de Gladstone et Dale est 0.038 (excellent). La manganokukisvumite est l'analogue a dominance de manganese de la kukisvumite; elle montre un lien etroit avec la lintisite.

The Crown emerald veins are somewhat enigmatic, displaying characteristics that are common to emerald deposits of tectonic-hydrothermal origin and of igneous origin. The veins cut the Fire Lake mafic meta-volcanic rocks, occurring within 600 m of an outcrop of Cretaceous S-type granite. Field work and vein petrography are consistent with a polythermal origin for the veins. The primary vein mineralogy is quartz and tourmaline with variable sized alteration haloes consisting of tourmaline, quartz, muscovite, chlorite and emerald. The veins weather a buff brown colour due to jarosite, scheelite and minor lepidocrocite, which were precipitated during the waning stages of vein formation. Microthermometic studies of primary fluid inclusions within emerald growth zones are consistent with emerald precipitation from H2O-CO2-CH4 ( +/- N-2 +/- H2S) bearing saline brines. The estimated fluid composition is approximately 0.9391 mol% H2O, 0.0473 mol% CO2, 0.0077 mol% CH4 and 0.0059 mol% NaCl ( similar to 2 wt.% NaCl eq.). Fluid inclusion and stable isotope studies are consistent with vein formation in the temperature range 365-498 T, with corresponding pressures along fluid inclusion isochore paths ranging from 700 to 2250 bars. These data correlate with a very slow uplift rate for the region of 0.02-0.07 mm/year.Emerald deposits are generally formed when geological conditions bring together Cr (+/- V) and Be. Cr and V are presumed to have been derived locally from the mafic and ultramafic rocks during hydrothermal alteration. The Be is most likely derived from the nearby Cretaceous granite intrusion. (C) 2002 Elsevier Science B.V. All rights reserved.

The first confirmed Canadian occurrence of the elbaite subtype of rare-element granitic pegmatite has been encountered within the O’Grady batholith, approximately 100 km NNW of Tungsten, N.W.T. The batholith, part of the Selwyn plutonic suite, is a mesozonal, hornblende-bearing, metaluminous composite intrusion with lesser amounts of pegmatitic granite and felsitic satellite dykes. On the whole, pegmatite bodies show a mildly NYF-type geochemical and mineralogical signature (allanite- and magnetite-bearing), but in the region of the pegmatitic granite, they grade toward a distinct LCT-type signature (elbaite-bearing). The melts parental to the pegmatite bodies were more voluminous, more alkaline, less aluminous and less reduced than is the norm for melts parental to LCT-type pegmatite. Differentiation of these melts sequentially produced hornblende granite, pegmatitic leucogranite and pegmatite, as shown by major-, minor- and trace-element geochemistry of K-feldspar, plagioclase, micas, tourmaline, amphibole and a variety of accessory phases. Lithium-mineralized pegmatite is recognized by the presence of multicolored elbaite, by lepidolite, and in the diversity of characteristic accessory phases such as danburite, hambergite, stibiocolumbite, pollucite, a nanpingite-like mineral, and bismutite. The various stages of the evolution of the batholith can be well documented in similar variations in mineral chemistry, and result in one of the few well-characterized case studies of the elbaite subtype.

The Little Nahanni rare-element granitic pegmatite group (LNPG; ca. 82 Ma) in the western part of the Northwest Territories, occurs as subparallel dike swarms over an area of ~11 × 5 km in the walls of a series of cirques dominated by schists of the Upper Proterozoic Hyland Group. These pegmatite bodies, up to a few meter wide, are divisible into spodumene-bearing and spodumene-free varieties that occur close together; some dikes split into these two variants. The two types are mineralogically similar. Both contain K-feldspar, plagioclase, quartz, mica (muscovite to lepidolite), columbite-group minerals, cassiterite, tourmaline, beryl, lithiophilite and garnet; they differ in the abundance of mica and accessory phases. The spodumene-free pegmatites have more mica, particularly lepidolite, than the spodumene-bearing variety. Apatite and montebrasite occur primarily in the former, whereas most lithiophilite is present in the latter. Sparse galena, titanian rutile, fluorite and helvite are also found in both variants. Subsolidus phases are zeolite-group minerals, microlite, and secondary phosphate minerals such as triploidite. Internal zoning in both pegmatites varies from complex to symmetrical. Where well developed, the zoning is typical from border through wall and intermediate to core zone. Quartz and the feldspars occur throughout the dikes. Micas and columbite-group minerals initially increase from the border to the wall zone and subsequently decrease toward the core, whereas tourmaline becomes less abundant toward the core. Spodumene and cassiterite first appear in the wall zone and become more abundant toward the core zone, whereas the reverse is true for beryl. Phosphate minerals exist mainly in the intermediate zone of the lepidolite pegmatites, and lithiophilite in the spodumene pegmatites. Garnet remains a trace mineral in all zones, with the exception of the core zone. where it is absent. Sporadic small cavities containing quartz, K-feldspar, apatite, Mg-rich beryl, elbaite and calcite are present in some dikes. The composition of the rock-forming minerals in both types of pegmatite is similar. An example of the chemical evolution of the minerals is shown by tourmaline, which becomes richer in Al and Li, but poorer in Mg, and shows decreasing Na/(Na + vacancy) and increasing Al/(Al + Fe) values from the schist to the inner (wall + intermediate) zone of the pegmatite. These trends, together with the changes in the abundances and paragenetic sequence of the major minerals, are interpreted to reflect an increase in the Rb, Cs, Li, F, P, Be, and Ta contents, and a decrease in the contents of Mg, Fe, and B contents, in the felsic liquids during crystallization.

A new occurrence of the rare mineral species ordonezite has been found at the Theodoso Soto tin mine, near Sapioris, Durango, Mexico. The average composition of the samples is (Zn0.98Fe0.02)(Sigma1.00)Sb2.00O6; the core of the crystals is slightly richer in Fe than the rim. The mineral is uniaxial (+), with all n greater than 2.30 (n(calc) is 2.38 at 589 nm); D-obs 6.66 g/cm(3), D-calc 6.67 g/cm(3). It is isostructural with ferrotapiolite, with a 4.668(2), c 9.269(6) Angstrom (from powder-diffraction data), space group P4(2)/mnm, and is twinned on {103}. Its crystal structure, refined to R = 4.1, wR = 4.3% using 163 observed reflections, is fully cation-ordered.

En septembre 1998, un des auteurs (WW) a decouvert un indice important de mineralisation en emeraude dans la region du lac Finlayson, dans le secteur sud-est du Yukon. L'indice de Regal Ridge est situe dans les roches metavolcaniques deformees de facon complexe dans le socle de Yukon-Tanana, pres du contact avec un pluton granitique mis en place au cretace moyen. Les cristaux d'emeraude se sont developpes ou des veines de quartz recoupent des niveaux micaces de l'unite schisteuse tardidevonienne de Fire Lake, mafique et a faible pendage. Au moins huit veines semblables ont ete reperees. Dans la plupart des cas, les veines sont entourees d'une masse de petits cristaux enchevetres de tourmaline foncee. Leurs sont associes localement de petites quantites de scheelite, et, dans les veines elles-memes, des sulfures. Une zone de sulfures epars coinciderait avec la zone a tourmaline, marquee par des produits d'oxydation ochres. Des cristaux de beryl vert atteignent 4 cm en longueur dans les zones a tourmaline et, dans certains cas, les veines de quartz. Certains des plus petits cristaux, et des portions des plus gros, ont une qualite gemme. La teneur en Cr (moyenne 3208 ppm) en fait le chromophore principal. Les donnees sur les inclusions fluides indiquent que la phase fluide responsable de la mineralisation avait une salinite maximale equivalente a 3% de NaCl. La composition isotopique de l'oxygene de l'emeraude est tres variable (entre 12.3 et 14.8‰), mais sans variation comparable dans les valeurs de 8D correspondantes (-57.3 et -59.8‰, respectivement), ce qui suppose une phase fluide isotopiquement homogene qui a amorce un echange isotopique avec l'encaissant sans toutefois atteindre l'equilibre. Les valeurs de δ 1 8 O du quartz et de la tourmaline des veines de quartz indiquent une temperature de formation d'environ 365 et 498°C. A la lumiere des donnees isochores des inclusions fluides, ces temperatures correspondraient a une pression entre 1.0 et 2.5 kbar, et donc une profondeur entre 3 et 7.7 km. La proximite du granite fait penser qu'il etait la source du beryllium, quoique sa teneur en Be est assez faible (entre 12 et 13.2 ppm). La source du Cr est le schiste (520 ppm Cr). Un âge 4 0 Ar/ 3 9 Ar d'un echantillon de mica du schiste, 109 Ma, pourrait temoigner de l'âge d'un rechauffement lie a la mineralisation, ou bien un refroidissement suivant la mise en place du granite, ou les deux.

An avoidable compounding of procedural and conceptual errors led to the generally held yet erroneous conclusion that "lyndochite" is equivalent to aeschynite-(Y). Instead, "lyndochite" is a minor chemical variety of euxenite-(Y), a conclusion reinforced by modern anecdotal and scientific evidence.

“Allanite” is a poorly defined collection of species belonging to the epidote group. In the past, “allanite” was defined as merely being lanthanon-bearing, but more recently, it is defined as being Ln-dominant at the A2 site. Species of the allanite subgroup include allanite-(Ce), allanite-(La), allanite-(Y), androsite-(La), dissakisite-(Ce), dollaseite-(Ce) and khristovite-(Ce). Lack of recognition of the recommendations of Nickel & Mandarino (1987), and of the relation between members of the subgroup with “allanite” in their species name and those without, has led to a number of errors in naming species and in use of the term “allanite”. Ten methods have recently been published describing how the relevant formulae may be calculated. Each is reviewed in conjunction with new observations on the behavior of Si, Cr, V, Mn 2+ and A-site vacancies. This evaluation results in a recommended procedure for the calculation of the formula involving a basis of 6 (M + T) cations and 12(O,F,Cl) + 1(OH). Recalculation of the formulae of published compositions of allanite-subgroup minerals shows that some apparently new species are better interpreted as intermediate solid-solutions between conventional end-members; there are, however, at least five potentially new species awaiting description.

Clearcreekite is a newly recognized polymorph of Hg 1+ 3 (CO 3 )(OH)·2H 2 O (along with the previously described peterbaylissite). The mineral is monoclinic, space group P 2 1 / c (14), with unit-cell parameters refined from powder data: a 6.760(4), b 9.580(4), c 10.931(4) A, β 105.53(5)°, V 682.1(6) A 3 , a:b:c = 0.7056:1:1.1410, Z = 4. The strongest six reflections in the X-ray powder-diffraction pattern [ d in A( I )( hkl )] are: 7.09(70)(011), 5.32(40)(111), 4.62(90)(012), 2.831(100)(023), 2.767(100) (211, 221), and 2.391(40)(040,204). The mineral is an extremely rare constituent in a small prospect pit near the long-abandoned Clear Creek mercury mine, New Idria district, San Benito County, California. The mineral is found as an isolated cluster of crystals in a shallow depression, associated with cinnabar and edoylerite, on a single specimen of brecciated silica–carbonate rock. Individual crystals do not exceed 0.17 mm in longest dimension and are subhedral, tabular, with major {001} and minor {010} forms. The mineral is transparent with a pale greenish yellow color and streak. Physical properties include: vitreous luster, uneven fracture, brittle, nonfluorescent, soft (grains punctured by an electron beam), calculated density 6.96 g/cm 3 (idealized formula). The mineral becomes dark brown-black and opaque when subjected to X-radiation, and the change is irreversible. Electron-microprobe analysis yielded 84.65 wt.% Hg 2 O. The empirical formula, derived from results of a crystal-structure analysis and of an electron-microprobe analysis, is Hg 1+ 2.92 (C 1.01 O 2.98 )(OH) 1.04 ·2H 2 O, based on O = 6. The idealized formula requires Hg 2 O 87.54, CO 2 6.16, H 2 O 6.30, total 100.00 wt.%. The infrared-absorption spectrum confirms the presence of both CO 3 and H 2 O. The mineral is named after the type locality.

Groat et al. (1998) proposed recently that wiluite, a boron-bearing variety of vesuvianite, is a new mineral species. Unfortunately, the authors did not refer to the results of numerous previous investigators of wiluite, which resulted in the inaccurate description of both the internal structure and

Ferrokentbrooksite, ideally Na 15 Ca 6 (Fe,Mn) 3 Zr 3 NbSi 25 O 73 (O,OH,H 2 O) 3 (Cl,F,OH) 2 , is a new member of the eudialyte group from Mont Saint-Hilaire, Quebec; it is the ferrous-iron-dominant analogue of kentbrooksite. It occurs as reddish brown to red, pseudo-octahedral crystals to 1 cm in diameter. Associated minerals include microcline, nepheline (partially altered to natrolite), fluorite, fluorapatite, natrolite, gonnardite, rhodochrosite, aegirine, albite, calcite, serandite, ancylite-(Ce), and catapleiite. It is transparent with a vitreous luster and a white streak. It is brittle, with a hardness of 5–6 (Mohs scale). It has no cleavage, no parting, and an uneven to conchoidal fracture. It is uniaxial negative with ω 1.6221(3) and e 1.6186(3). It is trigonal, space group R 3 m , a 14.2099(7) and c 30.067(2) A, V 5257.7(3) A 3 , Z = 3. The strongest nine X-ray powder-diffraction lines [ d in A( I )( hkl )] are: 7.104(38)(110), 5.694(50)(202), 4.300(43)(205), 3.955(31)(214), 3.391(51)(131), 3.207(31)(208), 3.155(31)(217), 2.968(100)(315) and 2.847(98)(404). The infrared spectrum of ferrokentbrooksite is given. An average result of two electron-microprobe analyses of the grain on which the structure was refined gave Na 2 O 11.96, K 2 O 0.44, CaO 7.99, MnO 3.88, FeO 5.08, SrO 0.45, Al 2 O 3 0.11, Y 2 O 3 0.58, La 2 O 3 1.51, Ce 2 O 3 2.51, Nd 2 O 3 0.53, Sm 2 O 3 0.11, Gd 2 O 3 0.17, SiO 2 44.70, TiO 2 0.09, ZrO 2 11.20, HfO 2 0.17, Nb 2 O 5 2.51, Ta 2 O 5 0.16, F 0.40, Cl 0.93, H 2 O 0.35, O ≡ F, Cl –0.38, for a total of 95.45 wt.%. The amount of H 2 O was calculated by stoichiometry from the crystal-structure analysis. The empirical formula of ferrokentbrooksite, based on 77.47 anions as determined in the crystal-structure analysis, is: (Na 13.05 REE 0.99 K 0.32 Ca 0.23 Sr 0.15 ) ∑14.74 (Ca 4.59 Mn 1.24 Y 0.17 ) ∑6 (Fe 2.39 Mn 0.61 ) ∑3 (Zr 3.00 Ti 0.04 Hf 0.03 ) ∑3.07 (Nb 0.64 Si 0.23 Zr 0.07 Ta 0.02 ) ∑0.96 (Si 24.93 Al 0.07 ) ∑25 O 73 (O,OH,H 2 O) ∑2.47 (Cl 0.89 F 0.71 OH 0.40 ) ∑2 ; D meas = 3.06(3) g/cm 3 , D calc = 3.06 g/cm 3 . Ferrokentbrooksite possesses the eudialyte structure, and has Fe as the predominant element at M (2) replacing Mn. Fe is predominantly five-fold coordinated, and bond-valence calculations indicate it to be divalent.