The crystal structure of the new mineral voggite, Na2Zr(PO4)(CO3)(OH).2H20 , from the Francon quarry, Montreal, Quebec, Canada, has been solved in order to determine the correct chemical formula, as conventional electron microprobe methods were found unreliable. The unit cell is monoclinic, I2/m, with a= 12.261(2), b = 6.561(1), c= 11.757(2)/~, 13= 116.19(2) ~ The structure consists of layers of edge-sharing Zr-O pentagonal bipyramids, separated by layers of Na-(O,H20) octahedra. The carbonate ion acts as a bidentate ligand in the Zr-O polyhedron, the third oxygen atom being bonded to the Na atom. The phosphate group is bonded to three different Zr atoms and to a Na atom. The Zr-O bond lengths vary from 2.067 to 2.283 (mean 2.140A), while Na-O are between 2.304 and 2.773, (or= 0.006/~, mean 2.480A). The carbonate and phosphate bonds are normal. It is inferred from the structure that the columns of octahedrally coordinated Na atoms can easily be broken apart when subjected to the heat generated by the electron microprobe beam, with the subsequent expulsion of water. This gives rise to 'mobile' Na atoms, which make quantitative electron microprobe analysis extremely difficult. The structure allows the 'liberated' Na atoms to move freely within planes parallel to (10T).

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Although radiological surveillance of patients with myelomeningocele allows recognition of upper tract changes, the effects of elevated outlet resistance on bladder compliance are not as readily reversible as the initial radiographic findings. The incidence of enterocystoplasty exceeds that reported for patients treated prospectively based on urodynamic findings, which should be considered in the treatment of these children.

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Chrisstanleyite, Ag2Pd3Se4, is a new mineral from gold-bearing carbonate veins in Middle Devonian limestones at Hope's Nose, Torquay, Devon, England. It is associated with palladian and argentian gold, fischesserite, clausthalite, eucairite, tiemannite, umangite, a Pd arsenide-antimonide (possibly mertieite II), cerussite, calcite and bromian chlorargyrite. Also present in the assemblage is a phase similar to oosterboschite, and two unknown minerals with the compositions, PdSe2 and HgPd2Se3. Chrisstanleyite occurs as composite grains of anhedral crystals ranging from a few µm to several hundred µm in size. It is opaque, has a metallic lustre and a black streak, VHN100 ranges from 371–421, mean 395 kp/mm2 (15 indentations), roughly approximating to a Mohs hardness of 5. Dcalc = 8.308 g/cm3 for the ideal formula with Z = 2. In plane-polarised reflected light, the mineral is very slightly pleochroic from very light buff to slightly grey-green buff; is weakly bireflectant and has no internal reflections. Bireflectance is weak to moderate (higher in oil). Anisotropy is moderate and rotation tints vary from rose-brown to grey-green to pale bluish grey to dark steel-blue. Polysynthetic twinning is characteristic of the mineral. Reflectance spectra and colour values are tabulated. Very little variation was noted in eleven electron-microprobe analyses on five grains, the mean is: Ag 25.3, Cu 0.17, Pd 37.5, Se 36.4, total 99.37 wt.%. The empirical formula (on the basis of ∑M + Se = 9) is (Ag2.01Cu0.02)∑2.03 Pd3.02Se3.95, ideally Ag2Pd3Se4. Chrisstanleyite is monoclinic, a 6.350(6), b 10.387(4), c 5.683(3) Å β 114.90(5)°, space group P21/m (11) or P21(4). The five strongest X-ray powder-diffraction lines [d in Å (I)(hkl)] are: 2.742 (100) (–121), 2.688 (80) (–221), 2.367 (50) (140), 1.956 (100) (–321,150) and 1.829 (30) (–321, 042). The name is in honour of Dr Chris J. Stanley of The Natural History Museum in London. The mineral and its name have been approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association.

Brodtkorbite, ideally Cu 2 HgSe 2 , a new mineral species, occurs in a telethermal selenide vein-type assemblage at the Tuminico Ia selenium deposit, Sierra de Cacho (Sierra de Umango) district, La Rioja, Argentina. The selenide assemblage also contains berzelianite, bellidoite, cadmoselite (mercurian, cuprian), chaméanite, crookesite, eskebornite, eucairite, ferroselite, hakite, klockmannite, a luanheite-type phase, trogtalite-kruťaite, tiemannite, tyrrellite, umangite and uraninite. Minor constituents are undefined phases that belong to the Cd-(Cu)-Hg-Se and (Co,Ni,Cu)-As-Se systems. The selenides occur as veinlets, as impregnations and as massive ores in calcite veins, and are hosted by altered (hematite-stained) amphibolites of the Sierra de Pampeanas, the Precambrian basement of the Precordillera terrane. Brodtkorbite was observed as anhedral grains; they range in size from 10 ϫ 20 up to 50 ϫ 100 m and as aggregates of composite grains up to 150 ϫ 250 m, commonly intergrown with berzelianite, tiemannite and (rarely) umangite and clausthalite. The mineral is dark grey, opaque, has a metallic luster, and a dark grey streak. VHN 10 ranges from 91.4 to 131 (mean 118) kg/mm 2 , which corresponds to a calculated Mohs hardness of about 2½ to 3. The density is 7.77 g/cm 3 and was calculated for the ideal formula with Z = 2. In plane-polarized reflected light, the mineral is white, is weakly to moderately pleochroic from pinkish to bluish white, and lacks internal reflections. It has a weak to strong bireflectance; the anisotropy is weak to strong with rotation tints from mauve-grey to yellowish grey. The reflectance spectra and color values in air and in oil are tabulated. The chemical composition, which was obtained with an electron microprobe, shows very little variation within individual grains and between grains. The average composition is: Cu 26.2, Hg 40.7, Se 32.9, total 99.8 wt%. This leads to an empirical formula (total atoms = 5) of Cu 2.00 Hg 0.98 Se 2.02 . Brodtkorbite is monoclinic, a 7.492(5), b 4.177(1), c 7.239(4) Å, ␤ 114.20(5)°, V 206.6(2) Å 3 , a:b:c 1.7936:1:1.7330, space group P2 1 /n (14). The strongest seven X-ray powderdiffraction lines [d in Å (I) (hkl)] are: 3.). The mineral name honors Milka Kronegold de Brodtkorb, Professor at the universities of Buenos Aires and La Plata, Argentina, for her outstanding contributions to the mineralogy and economic geology of Argentina. The selenide mineralogy at Tuminico is discussed on the basis of an extensive electron-microprobe study. The conditions of formation for brodtkorbite and the associated selenides are inferred from mineral stabilities and fluid-inclusion studies.

Alstonite, BaCa(CO3)2, is a mineral described almost two centuries ago. It is widespread in Nature and forms magnificent cm-sized crystals. Notwithstanding, its crystal structure was still unknown. Here, we report the crystal-structure determination of the mineral and discuss it in relationship to other polymorphs of BaCa(CO3)2. Alstonite is trigonal, space group P31m, with unit-cell parameters a = 17.4360(6), c = 6.1295(2) Å, V = 1613.80(9) Å3 and Z = 12. The crystal structure was solved and refined to R1 = 0.0727 on the basis of 4515 reflections with Fo > 4σ(Fo) and 195 refined parameters. Alstonite is formed by the alternation, along c, of Ba-dominant and Ca-dominant layers, separated by CO3 groups parallel to {0001}. The main take-home message is to show that not all structure determinations of minerals/compounds can be solved routinely. Some crystals, even large ones displaying excellent diffraction quality, can be twinned in complex ways, thus making their study a crystallographic challenge.

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