Notices of Trappean Minerals. 



59 



Mi 



Occasionally the masses of trap at Bound Brook have a thin 

 coating of white or bluish white prehnite, in which the radiated 

 arrangement has been exchanged for one that is indistinctly plu- 

 mose. Sometimes, however, it is nothing more than a thin scale. 



Prehnite froths before the blowpipe, and when the heat is con- 

 tinued, it melts into a compact colored globule. This globule is 

 usually light green, but in a specimen from Piermont, it is nearly 

 black, a fact which at first led me to doubt whether it was really 

 prehnite. But I have no knowledge of any mineral with which 

 it agrees so well as with this. 



Stilbite. — This mineral occurs at Bergen Hill, Paterson, 

 Bound Brook, and elsewhere in New Jersey. It is also found at 

 Harlem, and in the counties of Westchester, Putnam, and Rock- 

 land, N. Y. The primary form has been met with in Putnam 

 county, but the most common form in New Jersey, so far as my 

 observation extends, is that represented by the accom- Fig. 4. 

 panying figure. 



The crystals are often aggregated in various ways, 

 sometimes in the form of a sheaf. This is more com- 

 mon in those cases where they occur in cavities in the 

 trap or greenstone, and it is then often difficult to de- 

 termine the exact crystalline form. The mineral va- 

 ries from transparent to opaque, and the color is white, 

 yellowish, or red. The face M has a pearly lustre, but 

 it is not so perfect as the face P in the next species. 



Heulandite. — This often accompanies the preceding species, 

 which it closely resembles in many cases. The splendent pearly 

 lustre of the base of the prism will in general serve to distinguish 

 it. This character is very marked in the small but quite perfect 

 crystals found at Paterson and Bound Brook. At the latter lo- 

 cality I have noticed the primary form and the secondary, here- 

 with figured. 



Fig. 5. 



MonT, 130° 00' 



M on a, 146° 30' 



T on a, 148° 00' 



P on a, 111° 56' 



Mon/, 114° 20' 



Bound Brook, N. J. 



Berjen Hill, 

 N. J. 



