Diatomite coated with thin Fe films were obtained by the Chemical Vapor Deposition process. The resultant Fe-coated flaky diatomite particles had low densities (2.7–4.0g/cm3) and high saturation magnetization (93–157emu/g). Annealing treatment led to grain growth and an increased saturation magnetization. The high frequency properties of the composites consisting of Fe-coated flaky diatomite particles and wax were investigated. The permittivity and permeability increased with increasing flaky magnetic particles content in the composite and increasing the Fe weight percentage of the particles. The reflection loss of the composite was found dependent on the absorber material thickness, wax:flaky magnetic particles ratios, the Fe content, as well as the annealing treatment. At a thickness of 1mm, the composite records a minimum reflection loss of −18dB at 6GHz.