fenner: babingtonite from passaic county 557 



In Palache and Fraprie's measurements the angle between ij 

 and /i, the latter being a prismatic face of less prominent develop- 

 ment in their crystals, was measured as 89°18'. This probably 

 corresponds to the casts of nearly rectangular cross-section 

 which were often observed. No measurement of this angle 

 was attempted, as thin laminae of quartz frequently project 

 from the face corresponding to /?. 



The results of various tests on the New Jersey mineral are tab- 

 ulated above in comparison with the properties of babingtonite. 

 From this table it is evident that the mineral under discussion 

 agrees perfectly in all important respects with babingtonite. 



As a further confirmation etching-tests with hydrofluoric 

 acid were made upon cleavage-flakes (parallel with the base c) 

 of this mineral and of babingtonite from 

 Baveno, Italy (Nat. Mus. No. 86,183). r t> y,^/^ 



The two were placed together in a platinum ,) ^(j ^ ^ J '' i) 



basket and suspended for five seconds in ^ a ^ , (f ^S n 

 boiling commercial hydrofluoric acid. With ^ s \ ^ <3 ' fu a ^ 

 both specimens the etch-pits were very . d ^ ^^ n ! ^ H 

 minute and required careful observation ^s ^ \ fj<^ C f' 

 with a high-power objective to be satis- H \ \ ^ /\ ^ " 

 factorily studied, but, so far as could be ^ a i ^^ ^ i\ 



determined, the shape and size were the Q c 



same in the two instances. Figure 1 shows Fig. i. Etch-figures on 



their character. babingtonite, produced by 



Hintze and Dana cite but few locaUties ^ctionof hydrofluoric acid. 



. T 1 . Magnification 2o0 X. 



where babmgtomte has been found and it 



may be classed among the rarer minerals. The crystals are 

 generally of minute size. Its usual occurrence appears to be in 

 granite, syenite, gneiss, etc., apparently not generally as an 

 original igneous constituent, but associated with such minerals 

 as epidote, garnet, alkali feldspars, and quartz, in cavities. 

 Palache and Fraprie^ describe its occurrence at Somerville, 

 Mass., where it is found ".in veins and pockets composed chiefly 

 of prehnite, which traverse a large dyke of diabase." Quartz, 

 epidote, feldspar, laumontite, stilbite, chabazite and other 



•* C. Palache and F. R. Fraprie, loc. cit. 



