imon — Zincifi rout Chtys of Southwest Jfissouri. -il 



Thin sections of the tallow clays were examined with the 

 microscope without yielding any results worthy of note, beyond 

 that they appeared to be perfectly homogeneous, though no 

 general chemical formula? can be assigned them. They are no 

 doubt mixtures of zinc silicate with clay, formed by precipita- 

 tion from the reaction of zinc sulphide with hot siliceous 

 waters. 



The distribution of blende and calamine in Southwest Missouri 

 shows some interesting points for study. At Cartersville, Webb 

 City and Joplin, blende is the only ore of zinc mined. No 

 u tallow clays " nor calamine is found. It is however true 

 that at Webb City some of the miners call a grayish clay by 

 the name " tallow clay," but it is wholly unlike the other and 

 is improperly named. At Gran by, calamine is the principal 

 ore, while at Aurora, a new mining camp, both blende and cal- 

 amine are found ; blende being mined in one shaft, while not 

 far distant there will be other shafts from which calamine is 

 the only output. Lead sulphide is generally found associated 

 with the calamine here. At Aurora, as well as elsewhere 

 in southwest Missouri, " tallow " and " joint " clays are never 

 found in connection with blende deposits. 



The following partial section copied from the Missouri Geo- 

 logical Reports for '73 and '74, shows the general relations of 

 the u tallow " and u joint " clays to the calamine. 



3 feet red plastic clay. 



4 inches calamine with tallow clay. 



8 inches black sand and rotten dolomite. 



18 inches calamine with much dolomite. 



5 inches solid calamine. 

 (5 inches red clay. 



Many other sections might be quoted, which, while differing 

 in details. only, would show the same general relations of the 

 clays with the calamine. The red clay in the above repre- 

 sents " joint clay." These clays frequently contain crystals of 

 falena, and in the interior of several masses of " tallow clay " 

 have found in very small pockets crystals of calamine. 

 From the relations in position of the clays and calamines it 

 seems very probable that all the massive calamine once existed in 

 Southwest Missouri as "tallow clays,'' precipitated from solu- 

 tions. By filtration of waters the zinc silicate has been and is 

 still gradually being removed from the " tallow clays " and 

 crystallized as calamine. As the zinc silicate is removed from 

 the "tallow clays" they pass to the stage called "joint clays," 

 which differ from the former only in composition. 



In conclusion, I desire to call attention to the fact that a 

 clay similar in composition to the "tallow clays" has been 



