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In page Sienna:

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By the 1940s, the traditional Italian sources of the pigment were nearly exhausted. Much of today's sienna production is carried out in the Italian islands of Sardinia and Sicily, while other major deposits are found in the Appalachian Mountains, where it is often found alongside the region's iron deposits. It is also still produced in the French Ardennes in the small town of Bonne Fontaine near Ecordal.[6] It is important to note that the chemical composition of the umbers produced in France are distinctly different from the original siennas.[citation needed]