Decagonal C-60 crystals grown from a-hexane solutions correspond to an orthorhombic 1:1 solvate (a = 10.249 Angstrom, b = 31.308 Angstrom, c = 10.164 Angstrom). It forms with negative excess volume (-55.5 Angstrom (3) per formula unit) and transforms on heating into fee C60 (desolvation enthalpy of +50.6 kJ per solvate mole, close to the sublimation enthalpy for pure n-hexane) while n-hexane desorption from fee C60 is accompanied by an enthalpy of +48.6 kJ per solvent mole. Thus solvate formation is preferred to solvent adsorption. Orthorhombic C60 1 n-hexane undergoes no degradation when stored in air for 9 years at room temperature in the dark.