Kraus and Cook — Datolite from Westfield, Mass. 25 



hemi-pyramid ^{111 } and the positive hemi-orthodome £{102 J 

 are brilliant, giving good reflections. ^{111} appears as a dull 

 face in each instance. £{102} in addition to being dull was so 

 small that it could only be identified by zonal relationship. 

 The three types thus far considered show a marked resem- 

 blance to the Bergen Hill* dalolites. Type three also simulates 

 crystals from Toggiana.f 



Type four (fig. 6), which was observed on two well developed 

 crystals, possesses a tabular habitus. In some respects it resem- 



bles datolite crystals from the Lake Superior region described 

 by Osann.J The following forms were noted : 



a{100}, ft {010}, c{001}_, m {110}, m^jOll), #{012}, £{013}, 

 £c{102}, v{103}, n{ill\, vjlll}, e{112(. 



As may be seen from figure 6, the basal pinacoid <?{001} is 

 especially prominent in this type. Of the clinodomes, #{012} 

 predominates, — m^Oll} and £{013} being comparatively nar- 

 row faces. The orthodomes a? {102} and ^{103} are both dull 

 faces. 



In all thirty-two forms were observed. They are as follows : 



Pinacoids a{\00}, 6{010}, cjOOlj. 



Prisms m\ IffO}, r{230}, o{ 120}, £{130}. / 



Clinodomes m x {01 \ }, #{012}, ^{067}, 

 £{013}, m z {0-l-10(. 



Orthodomes sc{102}, -u{I03}, «{104}, fjl02j. 



Pyramids n{ 1 1 1 }, f}{ 121}, Qj 122}, 



v|lll}, bj223},6Jll2},X{Il3}, 

 fi{lU\, k{115}, n z {l'l'10\, M{122}, 

 i{l23},a{124},7r{231}, € {148}, 



^'{i-4-io}. 



Of these m y {067}, m z \0 m l m 10\, and ^{Tl-lO} are new for 

 datolite. 



On account of the excellence of the various faces, the observed 

 angles agree very closely with the calculated. The elements 



*E. S. Dana, this Journal (3), iv, 416, 1872. 



f Dana's System of Mineralogy. 



% Zeitschr. fur Krystallographie, xxiv, 543, 1895. 



