Ford and Bradley — Hetcerolite from Leadville. 603 



such as to make it very probable that this might be the case. 

 If all the silica present is considered to occur as a part of the 

 calamine molecule, it means that about ten per cent of the 

 material analyzed was that mineral. It is recognized that this 

 is a large amount to be present and still escape discovery, but 

 it is thought that the fibrous structure of the hetserolite might 

 very well serve to conceal this amount. The calculations 

 below have been made on this assumption, sufficient amounts 

 of zinc oxide and water being subtracted to form with the 

 silica the calamine molecule, H.,0.2ZnO.Si0 2 . 



Subtracting the 



equivalent of Reduced to 



H 2 0.2ZuO.Si0 2 100 per cent Ratios 



ZnO 37-56 —7-25 =30-31 33*73 0-414 =1-00 



Mn a 3 ._ 56-00 56-00 62'32 0*394 =0*95 



H„0 4-36 —0-81 = 3-55 3"95 0*219 =0*52 



Si"0„ 2-69 —2-69 



100-61 89-86 100-00 



If the above reasoning is correct, the formula becomes quite 

 clearly 2Zn0.2Mn 2 3 .lEt 2 0. The theoretical composition de- 

 rived from this formula is as follows : 



Theory 



ZnO.. 32-78 



Mn 2 3 ._ 63-60 



H 2 3'62 



100-00 



The analysis by Schaller, which was quoted by Palache, is 

 given below : 



1 2 Ratios 



ZnO 33-43 35-32 0*435 1*06 



Mn 2 3 60-44 63-85 0'405 



Fe 2 3 0-77 0-83 0-00 



SiO„ 1-71 



H 2 0- .... 2-47 



H 2 0+ .... 1-42 



i\ 



1-00 



100-24 100-00 



In the calculations given above the silica is disregarded and 

 no statement is made in the original discussion as to its prob- 

 able nature. The 3*89 per cent of water is also dismissed as 



