Bridgesite-(Ce), (IMA2019-034), was discovered at Tynebottom Mine, Cumbria, UK. It occurs as thin (1–2 μm) translucent blue crystals with a lath-like to acicular habit, aggregated into thin crusts and is associated mainly with brochantite, malachite, serpierite, devilline, gypsum, aragonite, jarosite, pyrite, lanthanite-(Ce) and undifferentiated iron oxyhydroxides, it is often intergrown with these other minerals. The lustre, hardness, cleavage and parting could not be determined, nor could density be measured due to crystal size. It has a pale blue streak and is brittle with a splintery fracture. Bridgesite-(Ce) is biaxial (–), shows no pleochroism and has refractive indices (white light): α = 1.526(2), β = 1.564(2), γ = 1.572(2) and 2V(calc) = 48.3°. The empirical formula calculated on the basis of 44 negative charges is Ca0.86REEΣ1.99Al0.07Cu5.95(SO4)3.99(SiO4)0.05(PO4)0.02(OH)11.52⋅8H2O. The idealised formula is CaCe2Cu6(SO4)4(OH)12⋅8H2O, requiring (wt.%): 3.91 CaO, 22.89 Ce2O3, 33.28 CuO, 22.33 SO3 and 17.59 H2O. Bridgesite-(Ce) is monoclinic, space group C2/m, a = 24.801(5), b = 6.3520(13), c = 11.245(2) Å, β = 114.51(3)°, V = 1611.9(6) Å and Z = 2. The five most intense X-ray diffraction peaks in the measured pattern are [d in Å (I, %) (hkl)]: 11.3 (100) (200), 6.391 (15) (201), 2.770 (8) (420), 3.194 (6) (402) and 4.858 (5) (310). The crystal structure was solved using single crystal data and refined to an R1 index of 5.86%. Bridgesite-(Ce) contains three distinct Cu sites containing Cu2+, two are coordinated octahedrally and one is square pyramidal. The octahedra form chains through edge sharing parallel to the b-axis which are linked by the square pyramid to form sheets oriented parallel to {100}. Sulfate tetrahedra decorate the sheets which are held together by interstitial REE3+, Ca2+ and hydrogen bonding. The structure is unique. Despite apparent similarity in chemical formula, bridgesite-(Ce) is not closely related to any other natural Cu-sulfate mineral. An FTIR absorption spectra is presented for reference purposes.

Pyrochlore group minerals have the general formula A16–xB16O48Z8–y·nH2O, with A mainly Na, Ca, Sr, REE, Th, U; B mainly Nb, Ta, Ti and Z being O, F, OH. In this study, pyrochlore specimens were examined from carbonatites at Argor, Carillon Dam, Chilwa Island, Fen, Lueshe, Oka, Mbeya, Meech Lake and Verity. Primary features include a background with little compositional variation, from core to rim, upon which are commonly superimposed narrow oscillatory zones, parallel to {111}. These zones are usually characterized by high Ta, in many cases coupled with U (here Argor, Meech Lake and Verity specimens), but Chilwa Island and Fen pyrochlores have little Ta and zonation is mainly by enrichment in Ce and Nb. Primary zonation may persist through high-temperature metamorphism (Meech Lake and Verity) and metamictization (Meech Lake). Oscillatory zones were generated by a disequilibrium system that cooled under tranquil conditions, signalling absence of magma turbulence and, in many cases, the end of crystal growth. Some fresh crystals (Oka, Fen) have no oscillatory zones, possibly the product of magma turbulence in space or time. Low-temperature effects may mimic those of primary high temperature and are especially characterized by replacement rims, pyrochlore-inpyrochlore veinlets and low A-ion totals (Carillon Dam, Lueshe, Myeba).

Effect of Ce addition on electric conductivity of Al alloys is investigated in this paper. Addition of proper amount of Ce leads to a remarkable improvement of electric conductivity. Adding Ce enhances the formation of binary, ternary, or quaternary compounds of Ce, Si, Fe, and Al and reduces the solution content of Fe and Si in the Al solution accordingly, well consistent with the Al lattice constant calculations and the Bragg models. Density of state adjacent to Fermi level of Al–Ce solution is obviously different from other solute atoms involving in La, Fe, and Si etc. and fairly similar with that of pure Al. Two possible contributions of Ce lead to the remarkable improvement of conductivity. First, Ce addition alleviates the lattice static distortion of Al solution and hence expands the average electrical free path. Second, Ce-induced alteration of electron energy band structure may intensify the effective electron number that participates conduction.