Diamond growth on non-diamond substrates initially requires a heterogeneous nucleation step on the substrate surface and, depending on the substrate material, the nucleation time may be very long and the nuclei density may also be very low, compromising the film quality. Seeding of substrates prior to chemical vapor deposition (CVD), typically using diamond grains, is commonly employed to increase nucleation of the growing film. Alternative nucleation methods are of great interest. In this work, we demonstrate the feasibility of using natural hematite to increase nucleation on silicon. This mineral in lamellae form is very soft and minimizes damage to the substrate surface. Hematite grains of a silica-rich phase improved the crystalline faceting and the coalescence of the growing diamond, indicating that complex oxides, such as iron silicates, may favor diamond nucleation. The nucleation density was approximately 0.8 x 10(6) nuclei cm(-2), which is a thousand times greater than that obtained on the 'unseeded' silicon surface. Samples 'seeded' with hematite grains of the silica-rich phase presented sharper peaks at 1332 cm(-1) (higher aspect-ratio), indicating a higher diamond quality.