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BULLETIN 131, UNITED STATES NATIONAL MUSEUM 



A twinned group of crystals resting in a cavity in galena from the 

 Last Chance mine is typical of many crystallized twinned groups 

 from the district and is consequently illustrated as an example in 



Pigs. 60-61.— 60, Cerusite. Squarish simple crystal from cavity in galena. Last Chance mine, 

 Wardner, Shoshone County. 61, Cerusite. Characteristic group twinned on wi(llO). From 

 cavity in galena. Last Chance mine, Shoshone County 



the drawing, Figure 61. The averages of the angles measured on 

 the several crystals of this group, are as given in the following table: 



Angles of crystal of cerusite, Figure 61, Last Chance mine, Normal position 



The McBride-Morrell lease on the Tyler upper workings in 1912 

 encountered a small body of rich carbonate ore in which much fine 

 crystalline cerusite appeared in places, mainly in the usual forms. 

 These included coarse heavy columnar masses of brilliantly lustrous 

 white material embedded in an ocherous impure manganese oxide; 

 reticulated masses of platy crystals; and fibrous forms, often irides- 



