You have gone to wonderful lengths here to obtain an XRD spectrum of the mineralogical summation of the specimen - Unfortunately this exceeds my expertise as I am not trained in geochemistry. My sense is that this array of minerals does suggest the possibility that these are indeed formed naturally, rather than by impregnation of a single human-applied chemical solution of either Calcium carbonate or silica.

The inclusion of the Mount keithite is (to my mind) a bit odd as that is a low temperature hydrothermal nickel sulphide associated mineral.... Silica, calcium, selenium and iron seem more like minerals that might be encountered in a surficial setting or a granite-based hydrothermal setting....