604 fenner: babingtonite from passaic county 



velopment. It is rather remarkable that, whereas the rectangu- 

 lar casts are found in various minerals — quartz, prehnite, pecto- 

 lite, datolite, albite — the lozenge-shaped casts have been observed 

 in quartz only, and no other minerals have been noticed in close 

 association (except possibly such as are of later origin). This 

 naturally implies a difference in conditions of deposition in the 

 two cases. 



In the previous paper the lozenge-shaped cavities were regarded 

 as due to babingtonite. Since then little new evidence has 

 been found which either confirms or disproves this view, but 

 one fact on which the conclusion was in part based has been found 

 to have less force than had been supposed. It had been observed 

 that cross-sections of the babingtonite crystals first discovered 

 exhibited lozenge-shaped boundaries, and in the new material 

 likewise this is frequently true, but careful examination raises a 

 doubt as to whether this is not a result of the manner in which 

 weathering has attacked the crystals. It seems probable, in 

 fact, that, in some cases, decomposition has acted in a peculiar 

 manner upon the crystal-surfaces and has tended to produce 

 lozenge-shaped forms from originally rectangular crystals. Less 

 weight, therefore, is now attached to this evidence. 



On the other hand, the measurements of the angles of the cav- 

 ities which were cited show very close agreement with the crystal 

 angle between the faces b (010) and g (210) of babingtonite. 



A number of the quartz pseudomorphs from McKiernan and 

 Bergin's quarry have been obtained and a series of new measure- 

 ments has been made with a contact goniometer. Some of these 

 specimens were kindly loaned by Professor Palache of Harvard 

 University and by Mr. Lovell of Paterson, and others were 

 secured from the foreman of the quarry. Although these pseu- 

 domorphs show sharp prismatic angles there was less agreement 

 among the measurements than had been expected. The average 

 of 56 measurements gave 61 5°, but there were variations ranging 

 from 57| to 66^°, and the two extremities of the same pseudo- 

 morph frequently showed a marked difference. 



The terminal faces of the specimens were small and much less 

 well-defined than the prismatic faces, and the angles were not 



