56 Notices of Trappean Minerals. 



after all, be accidental ingredients. The ratio of silica and lime, 

 which are the essential constituents, is nearly the same. This 

 mineral bears a close resemblance to Wollastonite, as described 

 by Dr. Thomson ; and the proportions of silica and lime are also 

 nearly the same. But Wollastonite contains from nine to ten 

 per cent, of soda. Moreover, in most of its properties, our mine- 

 ral bears a greater resemblance to the zeolite family than any 

 other; and if so, the only species with which it at all agrees in 

 its composition is that above mentioned. 



N Mr. James D. Dana in his work on mineralogy remarks, that 

 the stellite of Dr. Thomson is closely allied to natrolite. In an- 

 swer to this, it is enough to say, that natrolite contains twenty 

 four per cent, of alumina and sixteen of soda. Indeed, nearly 

 all the minerals of the zeolite family contain from twenty to 

 thirty per cent, of alumina; and none of them, I believe, except 

 stellite and apophyllite, contain less than eight or ten per cent, of 

 that earth. 



Thomsonite, for which the Bergen Hill mineral has been quite 

 generally mistaken, differs from it in its composition and in its 

 behavior before the blowpipe. Thomsonite swells up like borax, 

 becomes opaque and snow-white, but does not melt ; on the other 

 hand, all the specimens of supposed stellite from Bergen Hill 

 melt quite easily into a white enamel. I will not say that Thom- 

 sonite has not been found, or does not occur, at Bergen Hill ; but 

 I have not met with it in any of the specimens which I have 

 obtained from that locality. 



Apophyllite. — This mineral, which is very well described in 

 standard works on mineralogy, occurs at Bergen Hill and Pater- 

 son, in greenstone and trap, and at Harlem, New York, in gneiss. 

 The primary form, which is often found at the above localities, 

 is a right square prism. It differs from the other minerals which 

 it resembles, in cleaving easily in the direction of P, the cleavage 

 presenting a high pearly lustre. The faces of the prism have a 

 vitreous lustre, and are often striated longitudinally. The crys- 

 tals are usually transparent, but occasionally they are entirely 

 opaque and white ; and in one of my specimens the change from 

 transparency to opacity seems to be going on in the cabinet. 



Before the blowpipe this mineral exfoliates and finally melts 

 into a porous glass. The crystalline forms observed at the above 



localities are in all respects similar to those figured in elementary 



