370 Schaller — Siderite and Barite from Maryland. 



The pyramid iV= {551} is new for barite, 

 meas. (p), 84° 55', S4° 58', 84° 08,' 84° 45' calc. (p) 84° 45' 

 It occurs as very small faces. 



The general ideal view of these crystals 

 is shown in figure 3, though in detail the 

 size of the various forms varies consider- 

 ably even on the same crystal. There 

 are, also, unusually more faces (line faces) 

 in the prism zone than are shown in the 

 figure. Occasionally the crystals are flat, 

 parallel to the macropinacoid, but they are 

 usually of equal diameter, horizontally. 

 At times, too, one side of the terminated 

 end is much larger than the other. 



On account of the excellence of the 

 signals, an axial ratio was calculated from 

 the measurements. From the prism faces 

 values for d were obtained and values for 

 p Q and q were obtained from the pyramids 

 and domes (the ciwstals being measured 

 on the two-circle goniometer). From 44 

 values for a and 70 values for c, the following are obtained 

 which come very close to the accepted value : 



a = -8146 

 c = 1-3126. 



Barite. 



