Natural earths and ochres were amongst the first colourants ever to be used by humans, as they can be used almost directly from the ground with little processing. They owe their range of colours to their variable content of iron and manganese oxides, depending on which they are called ochres, siennas or umbers. Most often found in mixture with other pigments, they were rarely used in their pure form by Western European illuminators except for the red clay best known as 'Armenian bole', used as part of the preparatory layer for gold leaf.

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