NATURAL Inorganic Pigments The terms “earth color” and “earth pigment” are used to describe Natural Inorganic Pigments that are naturally occurring metallic salts, with significant quantities of clay and/or silica naturally mixed into them, such as hydrated ferric oxide and silica (raw sienna).
SYNTHETIC INORGANIC PIGMENTS Almost all of the inorganic mineral pigments used today are manufactured, or synthetic. A synthetic version of a pigment may be chemically identical to the natural form, but it is produced artificially rather than naturally. It may also be an entirely new pigment created from minerals.
An example of a naturally occurring inorganic mineral pigment would be genuine ultramarine blue, which is derived from the gemstone lapis lazuli. Synthetic ultramarine blue, on the other hand, is made by a modem process that combines silica, alumina, soda, and sulfur, the basic elements of the naturally occurring lapis lazuli.