The formation and the structural properties of Sn nanocrystals produced by ion implantation in thin ${\mathrm{SiO}}_{2}$ films was investigated by ${}^{119}\mathrm{Sn}$ conversion electron M\"ossbauer spectroscopy (CEMS), x-ray absorption spectroscopy (XAS), and transmission electron microscopy (TEM). Sn ion implantation was performed at 80 keV with a fluence of $1\ifmmode\times\else\texttimes\fi{}{10}^{16}{\mathrm{cm}}^{\ensuremath{-}2},$ positioning the peak of the implantation profile in the middle of the ${\mathrm{SiO}}_{2}.$ The annealing treatments were performed in the temperature range $800--1100\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ by rapid thermal processing. CEMS and XAS provided unique information on the local atomic and electronic environment of Sn in ${\mathrm{SiO}}_{2}$ allowing a detailed investigation of the effect of different annealing conditions. In the as-implanted state all Sn ions are oxidized (with both ${\mathrm{Sn}}^{2+}$ and ${\mathrm{Sn}}^{4+}$ oxidation states present), while annealing induces the formation of $\ensuremath{\beta}$-Sn nanoclusters. TEM showed that cluster sizes are in the range 7--17 nm. For clusters with average diameter $<10\mathrm{nm},$ XAS detected a reduction in coordination number and interatomic distances. Both XAS and CEMS indicate an increase in the static disorder in the metallic clusters. The investigated annealing treatments do not lead to a complete precipitation of Sn atoms in the metallic phase, leaving a fraction of them oxidized.