Abstract: Porous and non-porous compositions include diamond particles, non-diamond particles, or mixtures of particles consolidated with polycrystalline diamond. The composite compositions of the present invention may be formed by a process which includes the steps of preforming the particles into a preform having a desired shape, and consolidating the preform with polycrystalline diamond. The polycrystalline diamond is preferably formed using CVD techniques including application of sufficient microwave energy to maintain the preform at a temperature of between about 670.degree. and 850.degree. C. The preform may be rotated during a portion of the deposition process.