Thin solid films of C60 and C70 have been used as nucleating layers for the growth of diamond thin films on a variety of substrate surfaces, including metal, insulator, and semiconductors. Compared to other forms of carbon, such as graphite, amorphous carbon, soot, etc., it is found that the nucleation density on a C70 film is equivalent to that of diamond seeds themselves. On the other hand, diamond nucleation on a C60 film is less favorable. We argue from our experiments that the reason for C70 film to have such favorable nucleating properties is its chemical stability and geometry. A working model is proposed to explain the nucleation of diamond on solid C70 films. Application of this work extending to the growth of diamond on a wide range of substrates is also discussed.