1. raw sienna - Noun
2. raw sienna - Adjective
a medium to dark tan color
a yellowish-brown pigment made from untreated sienna
Source: WordNetA clay of limonite rich in iron oxide is the source of raw sienna and burnt sienna. Source: Internet
It is made by heating raw sienna, which dehydrates the iron oxide, changing it partially to haematite, giving it rich reddish brown colour. Source: Internet
This box at rights shows a variation of raw sienna from the Italian Ferrario 1919 colour list. Source: Internet