Sienna

:For the Italian city, see Siena.

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:For the vehicle, see Toyota Sienna.

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Sienna is a form of limonite clay most famous in the production of oil paint pigments. Its yellow-brown colour comes from ferric oxides contained within. As a natural pigment, it (along with its chemical cousins ochre and umber) was one of the first pigments to be used by humans, and is found in many cave paintings.

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Sienna, in and of itself, is sometimes referred to as "raw sienna", in order to differentiate it from "burnt sienna", which is a more common pigment than the raw form. The difference is in the process applied to burnt sienna, which is raw sienna heated to remove the water from the clay and redden its brownish colour.

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The name derives from the most notable Renaissance location for the earth, Siena, Italy, and is short for terra di Sienna, "earth of Sienna". The mines used to produce this sienna petered out in the 1940s. Much of today's sienna production is still in Italy's offshore islands, Sardinia and Sicily, while other major deposits are found in the Appalachian Mountains, where it often goes hand-in-hand with the region's iron deposits.

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Many of these deposits date back to the Precambrian, and are pointed to as evidence of the Snowball Earth hypothesis.

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See also:

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• SIENNA Technologies
• Sienna Plantation, Missouri
• clay earth pigment

Limonite: Limonite is a hydrated iron(III) oxide hydroxide of varying composition. The generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as limonite often contains a varying amount of oxide compared to hydroxide....

Clay: :For the town in the United States, see Clay, New York....

Pigment: :For the drug referred to as "pigment," see black tar heroin....

Sienna related Images and Photos (experimental)

Sienna II	Sienna Wave	Sienna Rise	Sienna Crest
Sienna Landscape	Port in Sienna 1912	No. 10 Brown Black Sienna on Dark Wine c.1963	Portrait of Actress Sienna Miller February 7 2007
Portrait of Actress Sienna Miller February 7 2007