In general, apatite crystals in glass-ceramics posses an isometric shape_1,2,3. However, in the system SiO₂-Al₂O₃-P₂O₅-CaO-K₂O-F^-, glass-ceramics with anisometric fluoroapatite crystals have been produced^4,5. In these glass-ceramics needle-like apatite crystals with a high aspect ratio (length: width) of up to 20: 1 can be obtained using high heating rates and a crystallization temperature of 1200°C. By the variation of the Ca: P ratio, the morphology of the fluoroapatite crystals can be controlled.