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Types Of Ochres

Yellow Ochre

Yellow ochre, is a form on hydrated iron(III) hydroxide (FeO(OH) nH2O). It's usually called limonite but limonite is not a true mineral name (although it's commonly used by geologists). Limonite is actually a mixture of different iron hydroxide minerals which typically form when iron-rich water encounters atmospheric oxygen (and typically helped along by Fe-fixing bacteria) - hence the name "bog iron" for sedimentary deposits of this mineral.

Red Ochre

Red ochre is derived from hematite (Fe2O3) which is oxidized iron and rusty red in color (rust and hematite are essentially the same thing). The name hematite comes from ???? (haima) the Greek word for blood (same root as hemoglobin) because of the color. Red oxide usually contains about 70% Fe2O3

Sienna

SiennaSienna is a brownish yellow containing about 60% Fe2O3 with some quantity of manganese oxide. It is named after sthe town of Sienna in Italy where a large deposit is located. Sienna is marketed in the raw and burnt (calcined) states.

Umber

Umber is a natural brown or reddish-brown earth pigment that contains iron oxide and manganese oxide. It is darker than the other similar earth pigments, ochre and sienna. In its natural form, it is called raw umber. When heated (calcined), the color becomes more intense, and the color is known as Burnt umber

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