Butler and Schaller — Minerals from Beaver Co., Utah. 421 



A closer examination of the specimen revealed pyramidal 

 crystals that could be separated from the surrounding material. 

 Several of these crystals were removed from the matrix and 

 measured. They showed a steep hexagonal pyramid, which 

 was strongly striated horizontally. Accurate measurements 

 were not possible, as the striations caused the crystals to 

 become rounded with consequent absence of plane faces. The 

 crystals were measured on the two-circle goniometer and p 

 angle determined for the pyramid faces. This angle corre- 



Fig. 1. 



Fig. 1. Wurtzite, o{2021}. 



sponds to that between the basal plane (absent on these crystals) 

 and the pyramidal faces. The values obtained are shown 

 below, the pyramid being the form o{ 2021 £ 



Measurement of o { 202 1 } wurtzite. 



Crystal No 1 2 3 4 



Average measurement 61° 62° 60° 61° Calc. 62° 06' 



The general habit of these crystals is shown in figure 1, 

 where the marked horizontal striae are also shown. 



The crystals of wurtzite dissolve readily in HOI, evolving 

 H 2 S. The solution contained abundant zinc and no other metal 

 was present in appreciable quantity. 



It may be noted that the zinc sulphides in this mine have the 

 property of tribo-luminescence or of giving off light when 

 scratched. This is so marked that sulphides of zinc can be 

 readily detected in the mine by drawing the point of the pick 



