The most common stones used for statuary in the classical world were marble and limestone, both of which would have been painted in antiquity. In general, marble was preferred over limestone; limestone was typically used in local settings, while marble might have been imported. Limestone was softer and easier to carve than marble, but marble’s crystalline structure provided it with a greater potential for polish. Most limestone and marble are white or off-white in color. Numerous colored stones (usually grouped under the heading of “colored marbles,” even though they are geologically heterogeneous) were known in antiquity. Colored stones were used infrequently in classical art prior to the Roman Empire, at which time quarries yielding black, gray, green, yellow, and purple marble, as well as variegated stones with dramatic veining, were actively exploited.
Marble and limestone architecture and statuary were typically painted in antiquity, although most of the pigments are not visible today. Modern scientific analysis, including the study of paint samples and the use of ultraviolet fluorescence (in which UV light reveals the presence of different pigments), has shed new light on materials and techniques of ancient polychromy. The paints were composed primarily of minerals, such as cinnabar (red), azurite (blue), and malachite (green); browns and yellows were composed from ochre, which was derived from soils with different mineral contents, such as iron. These colors were combined with bonding agents, such as egg (tempera) or wax (encaustic).