Agate samples from the Rancho Coyamito (Chihuahua, Mexico) were investigated to reveal the origin of their conspicuous violet coloured chalcedony bands. The comprehensive geochemical and spectroscopic investigations comprised trace element analyses by inductively coupled plasma-mass spectroscopy (ICP-MS), optical absorption spectroscopy, electron paramagnetic resonance (EPR) spectroscopy as well as cathodoluminescence (CL) mic...

Three oxide minerals belonging to the columbite group, including columbite–(Mn) (MnNb 2 O 6 ), columbite–(Fe) (FeNb 2 O 6 ), and fersmite (CaNb 2 O 6 ), were found in specimens from gem placers in Ratnapura district, Sri Lanka. We present results of chemical, structural and spectroscopic analyses, including the first Raman spectrum for natural fersmite. For columbite–(Mn) and columbite–(Fe), analytical results obtained before...

The cations of an ordered omphacite from the Tauern window were gradually disordered in piston cylinder experiments at temperatures between 850 and 1150 °C. The samples were examined by X-ray powder diffraction and then investigated using low-temperature calorimetry and IR spectroscopy. The low-temperature heat capacity data were used to obtain the vibrational entropies, and the line broadening of the IR spectra served as a to...

Crystals of the compound LiCo(SO 4 )OH were synthesised at low-hydrothermal conditions, and the crystal structure was determined and refined from single crystal X-ray diffraction data. LiCo(SO 4 )OH crystallises monoclinic, space group P 2 1 / c , Z = 4, a = 9.586(2), b = 5.425(1), c = 7.317(1) Å, β = 109.65(1)°, V = 358.3 Å 3 , wR 2 = 0.0485 (2215 unique reflections, 78 variables). The structure is built from chains of edge-s...

A multi-methodological study was conducted in order to provide further insight into the structural and compositional complexity of rare earth element (REE) fluorcarbonates, with particular attention to their correct assignment to a mineral species. Polycrystals from La Pita Mine, Municipality de Maripí, Boyacá Department, Colombia, show syntaxic intergrowth of parisite–(Ce) with röntgenite–(Ce) and a phase which is assigned to...