No. 2385. CRYSTALLOGRAPHW STUDY OF I) ATOLITE— SHANNON. 539 



EXPLANATION OF PLATES. 



Plate 103. 



Gnomonic projection of forms observed on datolite from Westfield showing distribu- 

 tion in zones. The zone numbers correspond to those used in the discussion of zones 

 according to Goldschmidt's Law of Complication. 



Plate 104. 



Datolite crystals from Westfield, Massachusetts. Large crystals showing type I 

 habit with characteristic mutual interference surfaces and molds of anhydrite crystals. 

 Crystals lightly coated with ammonium chloride. Natural size. Cat. No. 94253, 

 U.S.N.M. 



Plate 105. 



Datolite crystals from Westfiela, Massachusetts. Group of large crystals showing 

 characteristic habit and mode of aggregation. The large crystal in the center of the 

 group shows characteristic parallel growth. Crystals natural size. Lightly coated 

 with ammonium chloride. Cat. No. 86002, U.S.N.M. Gift of C. S. Bement. 



Plate 106. 



Datolite crystals from Westfield, Massachusetts. 



Upper. Group of crystals of Type 4 habit. The crystal figure 24 came from this 

 group. Coated with ammonium chloride. 1$ times natural size. 



Lower. Crystals lining cavity in vein of granular datolite. Coated with ammonium 

 chloride. 1$ times natural size. 



