Mineralogic Research Papers - Academia.edu (original) (raw)
Mineral quantifications are challenging on Ni-laterites: XRD analyses provide useful information on mineral species present in samples but with limitations in the precise quantification of complex mineral assemblages containing different... more
Mineral quantifications are challenging on Ni-laterites: XRD analyses provide useful information on mineral species present in samples but with limitations in the precise quantification of complex mineral assemblages containing different particle and grain sizes. The quantification of clay mineral rich samples presents particular challenges as described by Pevear (1989) and Reynolds (1989). Automated-SEM systems including MLA, Qemscan, and TIMA show also limitations with respect to the distinction of Mg-silicates with close chemical compositions (olivine, serpentine, talc, nontronite, saponite, pyroxene,…). MLA and Qemscan, and the associated software, provide analytical results as count proportions acquired by their respective detectors. These results are presented as element wt%. It should be noted, though, that these results are far from precise and need to be laboriously calibrated and converted in order to ascertain precise element wt% information that are necessary to calculate a structural formula of a mineral. The Mineralogic system allows very fast EDS analyses that provide element and oxide analyses that are acquired from Zeiss SEM analyses and are presented as precise element and oxide wt%. This Mineralogic methodology is a step change to methods employed by QMESCAN, MLA and TIMA. Mineralogic allows for each acquired EDS spectrum to have a matrix correction and peak deconvolution applied before a spectrum quantification. This methodology thus allows for accurate and precise elements quantification, which is subsequently classified using the designed mineral library. In contrast to MLA and Qemscan systems, Mineralogic data can be directly used to establish precise phase compositions, structural formulae, and to even distinguish mineral phases of very similar chemical compositions. The Mineralogic system enables the user to group mineral populations of minor chemical variation. The distinction and quantification of clay minerals and minerals that are grouped within the smectite group is only one field of application. An extensive database is currently under construction that allows a high-precision identification and distinction of minerals including those that were hitherto regarded as problematic with respect to their identification and, even more, quantifications.