4:20 Butler and SchaUer— Minerals from Beaver Co., Utah. 



present in equal molecular amounts, and in which a little ferric 

 iron is replaced by alumina. As the ratio of Fe 3 O a to A1,0 3 is 

 as 3:1, the formula can be written more exactly as 4Cu0.4PbO. 

 3Fe 9 O s .Al a O,.3SO,.16H a O. A comparison of the analysis with 

 the insoluble matter deducted and reduced to 100 per cent, 

 with the values calculated for the formula last given, is shown 

 below. 



Comparison, of analysis with calculated values. 



Analysis Calculated 



CuO 10-74 11-70 



PbO 32-50 32-80 



Fe a 3 19-13 17-61 



A1 2 3 403 3-75 



S0 3 . 23-60 23-54 



H„0 10-00 10-60 , 



100-00 100-00 



The water is all constitutional, as none was driven off below 

 250°. The actual results obtained are as follows: 



Loss of toeight of beaverite on heating. 



Tempt. 



Total loss 



110° 



0*04$ 



170° 



o-io 



250° 



0-14 



390°* 



3-72' 



590°* 



10-45 



* Heated in 



an electric furnace. 



The loss at 590°, as given, is higher than the true value, as 

 a little of the material was lost by the thermal couple acci- 

 dentally reaching into the crucible when some of the powder 

 adhered to the wires. 



No known mineral could be found with which beaverite 

 seems related, so that at present it must stand as an isolated 

 member of the sulphate group. 



Wurtzite. 



The hexagonal zinc sulphide, wurtzite, is present in consider- 

 able abundance in the primary ores of the Horn Silver mine. 

 The principal primary minerals of this deposit have been noted 

 above. The richer zinc ore in the hand specimen has the 

 general appearance of light honey-yellow sphalerite, but under 

 the microscope a portion is seen to be rather strongly bire- 

 fringent and some of this has the outline of pyramidal crystals. 



