We report on the synthesis of tin(IV) nitride with spinel structure, γ-Sn3N4, from the elements at high pressures and temperatures using a laser-heated diamond anvil cell, and on the Rietveld refinement of the product structure. The procedure described here is, in our opinion, the most reliable method of obtaining high-purity nitrides which are thermodynamically stable only at high pressures. Raman spectroscopy and powder X-ray diffraction were used to characterize the synthesis products. Pressure dependences of the Raman-band frequencies of γ-Sn3N4 were measured and used to determine its average mode Grüneisen parameter, 〈γ〉=0.95. Using this value, we estimated the thermal-shock resistance of γ-Sn3N4 to be about half that of γ-Si3N4, which, in turn, is moderately surpassed by β-Si3N4, known to be highly thermal-shock resistant.