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, mixture of varying proportions of iron oxide and clay, used as a pigment. It occurs naturally as yellow ocher (yellow or yellow-brown in color), the iron oxide being limonite, or as red ocher, the iron oxide being hematite.
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A naturally occurring brown siliceous earth, deriving its color from iron oxides and manganese oxide; used as a paint pigment.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
A naturally occurring brown siliceous earth, containing hydrated iron oxide with small amounts of manganese oxide; used as a pigment in paint; turns red to reddish-brown when calcined, and then is called burnt umber.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.
1. any of various natural brown earths containing ferric oxide together with lime and oxides of aluminium, manganese, and silicon
2. any of the dark brown to greenish-brown colours produced by this pigment
a. any dark, dusky, or indefinite colour
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005