Beaiimo?itite, Lincolnite^ and Heulandite. 423 



mineral, from different localities, assumes in some of its ex- 

 ternal characters ; appearing, perhaps, under some new mod- 

 ification of its primary form. 



A remarkable instance of the latter, has recently been pre- 

 sented in the case of the mineral examined by M. Levy, and 

 named Beaumontite.* This substance has long been familiar 

 to our American mineralogists, as the associate of the Hay- 

 denite found near Baltimore.! It has now become exceedingly 

 valuable, principally through the investigations of M. Levy, 

 who has thus supposed it to be a new substance. It is a very 

 beautiful mineral, and being extremely scarce, it will continue 

 to be highly prized by mineralogists, both here and abroad, 

 even if it should prove to be no new species, but only a rare 

 modification of a well known one. I believe it has not been 

 described in any of our late treatises on mineralogy, nor am I 

 aware that any notice has been taken of it in the American 

 Journal of Science. 



On comparing the crystals of this substance, with several 

 of those of the Heulandite of Nova Scotia, which presented a 

 modification rather uncommon, I was satisfied that they were 

 both derived from the similar replacement of the acute lateral 

 edges, and obtuse solid angles, of the same primary right 

 oblique angled prism ; the planes jT, which in most instances, 

 are small, being now so extended as to reduce the length of 

 the figure to nearly the same dimensions with its breadth ; 

 thus giving rise to what might, at first sight, appear to be a 

 square prism, terminated by two obtuse four-sided pyramids, 

 resting upon the opposite lateral faces of the crystal, as I have 

 endeavored to represent by the subjoined figure 2. The 



* M. l^evy read his paper before the French Academy of Sciences, (L'Institut. 

 1839, No. 313, p. 455.) An abstract of his communication may be seen in the London 

 and Ediuburs^h Phil. Mag. for February, 1840. 



t M. Levy's examination of the Haydenite, has confirmed the more general opinion 

 among mineralogists of its simple character. By some it had been allied with 

 chabaric ; but the early investigation of Dr. Hayden, showed a marked disagree- 

 ment between them in chemical composition, and Professor Cleaveland has proved 

 to be correct in the opinion which he gave of it in the first edition of his Mineralogy. 

 Our knowledge of this mineral will soon be complete, by the analysis of Mr. B. 

 Silliman, Jr. who now has it in hand. 



