The structure of a Si(111)-(7 X 7) surface capped by a 200 angstrom film of C60 was studied by grazing-incidence x-ray diffraction. The Si(111)-(7 X 7) reconstruction prepared in vacuum, including the loosely bonded ''adatoms'' on the surface, is preserved under the C60 overlayer. This result illustrates that C60 can be used as an inert cap for surfaces and suggests potentially interesting applications in surface science research and electronic device engineering.