ELSMOREITE, CUBIC WO3{middle dot}0.5H2O, A NEW MINERAL SPECIES FROM ELSMORE, NEW SOUTH WALES, AUSTRALIA

Abstract

Elsmoreite, WO 3 •0.5H 2 O (IMA 2003-059), is a new mineral species from the Elsmore tin deposit, Elsmore, in the New England region of northern New South Wales, Australia. The name is derived from the locality. It occurs as a white, microcrystalline powder (luster could not be observed) formed as a result of the oxidation of ferberite in the oxidized zone of weakly mineralized granitic pegmatite dykes containing Sn, W, Mo and Bi minerals, hosted in pegmatitic greisen veins in a granite stock. The mineral is cubic, space group Fd3m, with a 10.203(1) Å, V 1062.1(2) Å 3 , Z = 16, D calc 6.025 g cm-3 , using refi ned unit-cell data from natural material and the ideal formula WO 3 •0.5H 2 O. The density of the natural material could not be measured. The seven strongest lines in the X-ray powder diffraction pattern [d in Å(I)(hkl)] are: 5.884(100)(111), 2.944(78)(222), 3.075(62)(311), 1.804(23)(440), 1.964(17)(511), 1.725(14)(531) and 1.538(14)(622). Tungsten was the only cation detected by electron-microprobe analysis. An average of fi ve spot-analyses (W) on individual grains and a single thermogravimetric analysis for H 2 O gave 96.0% WO 3 and 3.3% H 2 O, yielding the formula WO 3 •0.44H 2 O, based on one W atom, and ideally WO 3 •0.5H 2 O. Elsmoreite is identical to the cubic synthetic phase of the same composition, and whose single-crystal structure is known. The structure is based on a defect pyrochlore lattice. Because of the minute grain-size of the natural material, its physical and optical properties were determined on synthetic WO 3 •0.5H 2 O. Microcrystalline octahedral crystals of WO 3 •0.5H 2 O are colorless with a white streak, translucent, and possess an adamantine luster, with a very high index of refraction, 2.24 ± 0.005 (white light). No luminescence was observed. The compatibility index (CI) is-0.164, which is classed as poor. Elsmoreite is brittle, has no apparent cleavage, a splintery fracture and a Mohs hardness of approximately 3. Crystals are octahedral, some of which seem to be twinned on the spinel law. The cubic tungstic acid is closely related to ferritungstite, alumotungstite and jixianite.

Synthesis and characterization of novel nanorod superstructures and twin octahedral morphologies of WO3 by hydrothermal treatment

“…Na 2 WO 4 has been obtained in cubic pyrochrlore form by Guo et al [46] and subsequent gentle heating resulted in cubic pyrochlore WO 3 thin films at a pH of 6.0. Interestingly, a recent report claims the discovery of a new natural mineral species, elsmoreite, with WO 3 $0.5H 2 O cubic pyrochlore structure, and octahedral morphology [47]. Our results are in agreement with this discovery, as far as the crystalline phase and morphology of the materials are concerned.…”

The crystal chemistry of elsmoreite from the Hemerdon (Drakelands) mine, UK: hydrokenoelsmoreite-3C and hydrokenoelsmoreite-6R

“…The HKE-3C phase crystallizes in space group Fd 3m, with a = 10.3065(3) Å and Z = 8 [A 2 B 2 X 6 Y ], which is typical for a material with the normal pyrochlore structure (Atencio et al, 2010) and is consistent with that reported for 'elsmoreite' (Williams et al, 2005) and synthetic WO 3 ·0.5H 2 O (Günter et al, 1989). A unit cell of the structure is shown in Fig.…”

Tuning of the crystal engineering and photoelectrochemical properties of crystalline tungsten oxide for optoelectronic device applications

“…32 These crystals are octahedral, and some seem to be twinned on the spinel law. In the same year, Guo et al 24 reported that octahedral tetragonal phase WO 3 (α-WO 3 ) ( Table 1c) particles were successfully produced by direct current (dc) arc discharge in Ar-O 2 gas.…”

“…19 Many crystalline hydrated tungsten trioxide compounds with the general formula WO 3 ⋅nH 2 O with n = 1/3 (0.33), 0.5, 0.75, 1, 2, etc., have been reported. 32 Their crystal phases are orthorhombic WO 3 ⋅0.33H 2 O, 33 45 Bi 2 WO 6 , 46 PbWO 4 , 47 and CdWO 4 , 48 have been studied for different applications. For example, CuWO 4 has been studied for PEC water splitting 6b,44 and Bi 2 WO 6 for CO 2 reduction.…”