240 



REPORT OF NATIONAL MUSEUM, 1899. 



The natural colors of the ochers is dependent on the degree of hydra- 

 tion and oxidation of material and the kind and amount of impurities. 

 In a general way the hematites are of a deep-red color (Specimen No. 

 56075, U.S.N.M.), while the limonites are yellow or brown (Specimen 

 No. 61101, U.S.N.M.). Either color is liable to shade variations, 

 according to amount and kind of impurities. The colors are intensi- 

 fied or otherwise varied by roasting (Specimens Nos. 63056 and 63057, 

 U.S.N.M.). 



Artificial ochers are produced by roasting iron pyrites (sulphide of 

 iron) or an artificial sulphate (green vitriol) (Specimen No. 61122, 

 U.S.N.M.). (See under Py rite.) The materials known commercially 

 as rouge, crocus, and Indian red are quite pure ferric oxide, pre- 

 pared by roasting pyrite or by other artificial means. 



Composition of ochers in their natural condition. 



a A part of the iron in a ferrous condition, 

 clron exists mainly in a ferrous condition. 



6 Contains also some manganese. 

 d Contains much manganese. 



Composition of manufactured mineral paints. 



a Made from red fossiliferous ores mined at Atalla, Alabama, and Ooltewah, Tennessee. 

 6 Made by Iron Clad Paint Company, of Cleveland, Ohio, from ore mined in Wayne County, Ne\ 

 fork. 



c From ore mined at Lake Superior, Michigan. 

 d Ore from Jackson mlae, Michigan. 



