OCHRE, (Fr. ocre, from Lat. ocrv, from Gk. 6);rpa, yellow ochre, from kpitc, dchros, pale). A mineral paint consisting of clay colored with some oxide of iron, rarely of manganese. in various proportions, giving to the clay a lighter or deeper color. Ochres are common in many geological formations. more especially the young er ones, in which the materials are consolidated. For use the material is dried, ground. and mixed with oil. The commercial value of the material depends on its shade of color, the regularity of distribution of the iron coloration. and the quan tity of oil which is required to mix. it up. Cal cination is sometimes resorted to in order to produce the desired tint ; the operation adds miteh to the depth of color, by increasing the degree of oxidaticat of the contained iron. The common color of ochre is yellow. Umber and sienna differ from ochre in containing manganese in addition to the iron. Raw umber has a brown color, while burnt umber is of a red tinge.
1Zaw sienna is brownish yellow, hut when burned it yields a rich russet brown pigment. The finer grades of ochres are used by painters. the coarser by carpenters for marking out their work, etc. Common ochre is found in many parts of the United States. The most important States producing it are Alabama. Arkansas, California, Georgia. Massaelin sett s. Missouri. New York, Pennsylvania, Texas. Vermont, and Virginia. Umber and sienna are produced by New fork, Pennsylvania. and :Mis souri, but much is also iMported. France leads the world in the production of ochre. with Ger many second. and the United States third. Con sult : Volumes of Mitierui Resources, issued by United States Geological Survey (Washington. annually) : Fulls "Report on Metallic Paint Ores Along the Lehigh River." -I annul Report of the Geological surrey (11a rrisburg • 188(i).