fenner: babingtonite from passaic county 603 



what different appearance from that presented by the extremely 

 thin laminae. In still others a cell-like structure of rectangular 

 partitions has been built across the cavities. In such types 

 anhydrite may have been the original filling, but no trace of 

 either mineral has been detected in them. 



The formation of the laminae and ridges and partitions seems 

 best referable to the action of solvents upon planes of easy 

 solution in the crystal structure, with the simultaneous deposi- 

 tion of other minerals. Such solution-planes would most likely 

 correspond to cleavage-planes, although not necessarily so. 

 Anhydrite, as is well known, has three easy cleavages at right 

 angles to each other. According to Dana and Hintze, babing- 

 tonite has but two cleavages, which are parallel to 001 and 010 

 and include an angle of 92° 36', but it has been found by exami- 

 nation of small cleavage-fragments under the microscope that 

 in reality four are probably present. Three of these make angles 

 with each other which do not differ appreciably from 90°. These 

 cleavages have been observed both in the New Jersey mineral 

 and in National Museum specimens from Italy and Norway. 

 Therefore it does not appear practicable at present to differentiate 

 the casts on the basis of rectangular parting-laminae. 



In these approximately rectangular cavities the babingtonite 

 crystals appear to have been of prismatic or tabular habit, with 

 a terminal plane cutting the other two at nearly right angles. 

 It cannot be stated definitely which crystal-faces are represented, 

 but, as suggested in the former paper. Dauber's g (210), h (110), 

 and c (001) appear probable forms. These are figured by Hintze 

 as faces of prominent development in babingtonite from Arendal 

 and Herbornseelbach and the included angles differ only slightly 

 from 90°. Crystals bounded by these three planes are of simpler 

 fomi than babingtonite ordinarily shows, but, considering the 

 well-known variations in this respect which many species exhibit, 

 this does not appear of serious importance. 



Thus far the casts of rectangular form only have been treated 

 in this article, and it remains to consider those of lozenge-shaped 

 cross-section. The latter are also of frequent 'occurrence in the 

 deposits and are often associated with those of rectangular de- 



