66 Mr Alger on Neiv Localities of "Rare Minerals. 



Beaumontite of Levy, and Lincolnite of Hitchcock. — In a paper 

 read before the Boston Society of Natural History, and since pub- 

 lished in their Transactions, and in the American Journal of Science 

 (vol. xlvi., p. 235), I gave my reasons for classing these two mine- 

 rals with Heulandite. That Beaumontite is Heulandite, I believe, 

 is no longer doubted in this country or Europe. An analysis of the 

 mineral by M. Delesse, has appeared since the publication of my 

 paper,* and it agrees with all the other analyses of Heulandite, ex- 

 cepting in the slight excess of silicic acid. In this respect, it offers 

 an example analogous to that of the variety of Chabasite, called 

 Acadiolite, in which the silicic acid forms a larger atomic proportion 

 of the mineral, without causing any appreciable variation in the 

 angles of the crystals. As to Lincolnite, I must think that the 

 various papers, that have been called forth in relation to it, since 

 my first communication appeared, have established its indisputable 

 identity with Heulandite. 



Peculiarities in the modifying planes,"!" have given rise to a secon- 

 dary form, rarely observed in Heulandite. These consist in the en- 

 largement of the planes / (Phillips), or e (Dana), so as nearly to 

 obliterate the primary planes M; being, in fact, the reverse of what 

 we usually observe in Heulandite from other localities. In the 

 measurements by Professor Hitchcock and Professor Shepard, the 

 angle of / on T was mistaken for that of M on T, and in the figure 

 given by Professor Hitchcock, it is evident that the planes lettered M 

 should be /. The true value of / on T is 115° 10' (Dana) ; Pro- 

 fessor Shepard's last measurements made it 116° 17/ 



Ledererite. — I am compelled at last to declare my conviction, that 

 the specific nature of this mineral can no longer be maintained. 

 Connell's analysis of an Irish Gmelinite, which agrees with Ledere- 

 rite in all its physical and crystallographical characters, has shewn 

 also an identity in chemical composition. The phosphoric acid, de- 

 tected by Mr Hayes, must be viewed as an accidental constituent, 

 varying probably in diff'erent crystals, or, in some of them, not ex- 

 isting at all. Some of the Zeolites, in the Nova Scotia trap, have 

 been found associated with small crystals of phosphate of lime, and 

 it is not impossible that some of the minutest of these may have in- 

 tercrystallized with the Ledererite. We regret that we have not 

 been able to obtain other specimens to enable Mr Hayes to give it a 

 re-examination. For comparison, I subjoin the analyses of Ledere- 

 rite and Gmelinite. 



♦ Ann. de Chim. et de Phys. for 1843, t. ix., j). 395. Phillips's Min., p. 627. 



t For the figures see Am. Jour, of Science, vol. xlvi., p. 234, and vol. xlrii., 

 p. 416. Corroborative evidence of the correctness of my opinions, by the edi- 

 tors of the Am. Jour, of Science, may be seen at the pages here referred to. 



