Mixed-oxide powders of tin and tungsten were made by heating various mixtures of SnO and WO3 powders, corresponding to the nominal formula SnxWO3+x with x between 0.5 and 2.0, in an argon atmosphere at 600 °C for 15 hours. The α-SnWO4 phase was the result of heating of an equimolar mixture of SnO and WO3 powders. In addition to 119Sn Mössbauer experiments, X-ray diffraction and Raman spectroscopy were used to study the phase structures of the mixed-oxide powders. Mössbauer spectra from all samples show a small peak at ∼0mm/s from phase(s) like rutile SnO2, and a larger peak doublet centred at ∼3.4mm/s from the α-SnWO4 phase, where tin is in the form Sn4+ and Sn2+, respectively. Another peak doublet centred at ∼3.0mm/s was needed to obtain reasonable fits for samples with x ≥ 1.3. This doublet originates from an undocumented phase where tin is also in the divalent form Sn2+. 119Sn Mössbauer spectroscopy made it possible to reveal the relative amounts of the two valence states of tin in the mixed-oxide structures. Raman spectroscopy as the other probe for "local" structures was insensitive to reveal the changes in the phase structures between different mixed-oxide samples up to x = 1.72, but an extra peak at ∼890cm-1 in the Raman spectrum from the sample with x = 2.0 indicates also the presence of the undocumented phase.