Final answer:
The cosmetic classification that requires sifting to remove coarse, gritty particles is a powder. Sifting ensures the homogeneity and appropriate texture for cosmetic application.
Step-by-step explanation:
The cosmetic classification that requires sifting until free of coarse, gritty particles is a powder. In the context of cosmetics, powders can be composed of fine particles that need to be homogeneous in size and feel pleasant on the skin. Therefore, they are sifted to remove any larger, gritty particles that would be undesirable in the final product. In contrast, ointments are semi-solid preparations that typically do not contain gritty elements; emulsions are mixtures of two immiscible liquids where one is finely dispersed in the other; and suspensions are heterogeneous mixtures where solid particles are dispersed in a liquid but could settle upon standing. Suspensions may require shaking or mixing before use to ensure uniform distribution of the particles throughout the liquid but not necessarily sifting.