^71] RED AND YELLOW OCHRE. 41 



Nimerous specimens of clays from localities not specially men- 

 tioned here are in the collection of the Survey awaiting examina- 

 tion as to their practical value, and will be reported on hereafter. 

 Potter's clays are mentioned by Harper as occurring in several 

 localities along the Mississippi bluff; but no specialities concerning 

 their kind and geological position are given by him. 



71. Not un frequently, there are found within the Orange Sand 

 formation clays so highly colored as to become of more importance, 

 as pigments or paints, than for any other purpose. In numerous 

 localities, these colored clays have been used for painting houses or 

 fences, in the same manner that the white clay of Tishomingo has 

 been employed as a whitewash. 



It has been mentioned (164) that on the Memphis & Charleston 

 Railroad, near Iuka, masses of red clay were found imbedded in 

 the white mass ; and that red veins are frequently visible in 

 other localities. A remarkable deposit of clay impregnated with 

 peroxide of iron so strongly as to make it valuable as an ochre or 

 paint, occurs further north, on S. 30, T. 2, R. 11 E., near Mr. 

 Biggs' place. The stratum crops out, with a visible thickness of 

 15 feet, forming the bank of a small stream : it is overlaid like the 

 white pipeclay, by strata of ferruginous pebble conglomerate. The 

 color of the mass is a dull red, resembling that of Burnt Siena 

 earth, with somewhat more of a reddish hue ; it contains occasional 

 small veins or lenticular masses of perfectly white clay, resembling 

 the rest except in color. It is but indistinctly stratified, and cleaves 

 into irregular, massy fragments, the cleavage-planes often being 

 almost black ; it is peculiarly smooth or "greasy" to the touch, and 

 when handled assumes a polished appearance. It writes readily 

 on wood or paper, making a brownish red mark, and might easily 

 be cut into pencils. When moistened it exhales a strong clay odor, 

 and on being kneaded forms a plastic mass, which no doubt might 

 be worked on the lathe after due seasoning. On being crushed it 

 forms, with either oil or water, a paste so perfectly uniform and 

 smooth, that the eye is unable to detect any coarse particles on a 

 white surface painted with it, even when nothing more than a 

 wooden pestle has been used in the process of mixing. It is there- 

 fore a most eligible material for the manufacture of paint, since it 

 requires so little mechanical preparation. The color, as has been 

 stated, very nearly resembles that of Burnt Siena earth (a reddish 



