176 GEOLOGICAL RECONNOISSANCE 



might become useful as a common paint, though the amount of oxide of 

 iron present is rather small. 



No. 3G. Argillaceous rock, from the crevices of the New York company's 



lead mines, Marion county. 



Massive, amorphous; color pale yellowish-white and reddish-white; 



very light and soft; can be cut with a knife like chalk; on the surface, 



covered with a crust of peroxide of iron; powder of a pale reddish cream 



color; assumes on ignition a fine pink color. 

 Composition, dried at 230 deg. F: 



Insoluble silicates, mainly a very fine soft clay 96.095 



Peroxide of iron, and alumina, with a little phosphoric acid. 1.795 



Lime 0.148 



Manganese, magnesia, and potassa traces 



Water 2.055 



• ' 100.093 



The air-dried rock lost 0.73 per cent, of moisture at 230 deg. F. 



No. 37. Argillaceous rock, associated with galena, at Houghton's dig- 

 gings, Lawrence county. 



Bears a great resemblance to the preceding rock in general appearance. 

 Its origin is probably the same, occurring, as it does, under similar condi- 

 tions; but it appears to have come in contact, after its deposition, with liquids 

 containing oxide of zinc in solution. The presence of about 8 per cent, 

 of oxide of zinc in this clay points to the deposition of carbonate of zinc 

 somewhere near Houghton's lead diggings. 



Massive, amorphous; color ochre-yellow; light and soft; can be cut with 

 a knife like chalk; covered on the surface with a thin layer of red clay, 

 resembling No. 35; powder of a dirty grayish-yellow color. 



Composition, dried at 230 deg. F: 



Clay and sand 74.841 



Peroxide of iron 2.383 



Alumina 8.213 



Phosphoric acid 0.214 



Oxide of zinc, with trace of manganese 8.262 



Carbonate of lime 0.709 



Carbonate of magnesia 1.337 



Water and carbonic acid (?), expelled by heat- • 3.844 



99.803 

 The air-dried clay lost 3.92 percent, of moisture at 230 de°\ F. 



