Earth pigment

An earth pigment is a naturally occurring colored mineral material, usually an iron oxide or clay, ground for use in paints and other materials. Its mineral composition gives it characteristic hues and durability.

Iron oxide: A family of iron-and-oxygen compounds that includes common red, yellow, and brown pigments. Iron oxides supply many earth pigments’ characteristic colors.
Pigment: A finely divided colored material that imparts color to another substance. Earth pigments are a natural mineral subset of pigments.
Cave painting: A painted image made on a cave wall or ceiling, often using mineral pigments. Earth pigments appear in some of humanity’s earliest surviving paintings.
Synthetic iron oxide pigment: A manufactured iron oxide colorant produced under controlled industrial conditions. It can reproduce earth-pigment hues with more consistent composition and color.
Ochre: A natural earth pigment colored by iron oxides, commonly yellow, red, or brown. Ochre is the best-known family of iron-rich earth pigments.
Calcination: Heating a solid to high temperatures to cause chemical or structural change. Heating yellow iron-rich earth can transform it into red pigment.
Fresco: A wall-painting technique in which pigments are applied to wet plaster. Earth pigments suit fresco because many remain stable in alkaline plaster.
Lake pigment: An insoluble pigment made by fixing a soluble dye onto an inert substrate. Lake pigments derive color from dyes rather than naturally colored mineral particles.
Clay mineral: A fine-grained mineral, commonly a hydrated silicate, that becomes plastic when wet. Clay minerals often form the matrix that holds pigment particles together.
Color: The visual sensation produced by light interacting with an object and the visual system. Mineral composition and light absorption produce an earth pigment’s perceived hue.

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