424 



Alger on the Identity of 



planes a a', being carried to the extreme, so as to entirely 

 obliterate the edge formed by the planes M and T, of the 

 right oblique prism, fig. 1, — the pyramids thus resulting are 

 very beautiful in both minerals, particularly in the Beaumon- 

 tite, and they present the same characteristic vitreous lustre, 

 contrasted with the soft, pearly white reflection of the planes 

 P, which we always observe in the crystals of this mineral 

 from other localities. Both minerals, however, present shades 

 of brown and yellow. On further comparing their hardness 

 and pyrognostic characters, and failing also to obtain any 

 other cleavage in the Baltimore specimens, than that well 

 known in Heulandite, I could have but little doubt that M. 

 Levy, (unless he had described some other very analogous 

 mineral from this locality, wliich I have not seen,) had been 

 misled by its unusual crystalline form, and, instead of making 

 known a new species, had only given us the wrong characters 

 of an old one. 1 am sure that he would not have been led 

 into a mistake of this kind, had the crystals examined by him 

 presented those gradual changes which have ultimately given 

 rise to the figure which he supposed to be the primary right 

 square prism of the Beaumontite, and which we so readily 

 observe in the crystals from Nova Scotia. 



This is the onhj respect in which the Heulandite from Nova 

 Scotia, and M. Levy's mineral, diflfer from each other ; and 

 it is in reference to this single peculiarity in the approximation 

 of the crystals of the Nova Scotia mineral to a right square 

 prism, that it has hitherto commanded an especial interest 

 among our mineralogists. I had never seen the decrement 

 carried so completely out in the crystals from any other local- 

 ity, until these beautiful specimens met my eye from Bahi- 

 more. The smaller replacements b b', which are often seen 



