When sourcing Calcium Hydroxyapatite, you must prioritize the Purity Level (typically ≥99%) and the Ca/P Atomic Ratio, which should be approximately 1.67 to ensure biological similarity to natural bone. Additionally, the Particle Size (D50) is critical; nano-grade (20-100nm) is preferred for high-end biomedical coatings, while micro-grade is suitable for dental fillers or chromatography. Ensure the Crystallinity Index matches your specific application needs, as it affects the material's resorption rate.