In this paper, we disclose a novel biomaterial with a considerable capacity for cell growth and bone mineralisation. The biomaterial is manufactured by sintering diatom (Cyclostephanos sp.) frustules under two different moulding pressures at temperatures of 1100 °C over varied times (5–72 h). The in vitro cell biocompatibility of the biomaterial was initially assessed using human kidney HEK cells and MDA-MB-231 breast cancer cells. These cells attached to the biomaterial and were in fact observed to grow preferentially on the diatomaceous biomaterial in larger densities than on commercial cell culture plates over longer time-periods (>15 days). As part of a bone-regeneration proof-of-principle study, cell biocompatibility of the material was also tested in vitro using pre-osteoblast MC3T3-E1 cells over 21 days and osteoblast activities were measured by staining with von-Kossa stain for mineral deposits. Cells had attached to the biomaterial on day 2 and showed positive staining for mineral deposits after the 21-day period. The material was also noted to be autoclavable and reusable without any adverse effect observed on subsequent cell cultures.