454 Prof. B. Silliman on some American Minerals. 



Silica . 4618-48 34*47 p.cafc 

 Alumina 7708-00 57-55 

 Lime . 1068-06 7*98 



13394-54 IGO'OO 



99-50 



3R0, 12Ar03, 8Si03=3RO, 2Si03 + 6{2Art)3, SiO^). 



Possibly a new analysis may bring these species together. 



The species corundellite occurs not only in the broad fo- 

 liated masses above alluded to, but also in small scales disse- 

 minated throughout the mass of granular corundum at Union- 

 ville, Pennsylvania, and in this form is quite abundant. Not 

 unfrequently these scales have a delicate shade of violet, espe- 

 cially when wet. The rock is difficult to break, and the co- 

 rundellite appears to adhere very strongly to the associated 

 minerals, and the laminae are not so easily separable as in the 

 foliated masses*. 



Euphyllite. 



This beautiful pearly white mineral is found associated with 

 black tourmaline and corundum at Unionville, Pennsylvania. 

 Form, apparently hexagonal; cleavage, eminent on basal 

 plane; the lamina) not so easily separable as in mica. Hard- 

 ness, 3. Gravity, 2-963. Lustre of sides, faint pearly; of 

 basal plane, very brilliant pearly, resembling Heulandite, but 

 perhaps more brilliant even than in that species. Colour of 

 cleavage, face pure white, of sides grayish, sea-green or whitish. 

 Laminae, rather brittle, inelastic, and quite transparent. , 



B. B. exfoliates, fuses on edges of thin laminae, and emits a* 

 stronger light than either of the corresponding species. In 

 the matrass it evolves water, and gives a reaction for fluorine. 

 No reaction for lithia or boracic acid was obtained, but it 

 gives a soda-yellow to the flame. 



The qualitative analysis of this mineral gave silica, alumina, 

 lime, magnesia, soda, water and fluorine. 



The quantitative analysis was conducted by Mr. J. J. Crooke, 



* The species barsowite (G. Rose) appears in the Ural to hold the 

 same geognostic relations to corundum as do the minerals of the present 

 memoir in this country. Its composition however is quite distinct (silica, 

 49*01 ; alumina, 33-85 ; lime, 5-46; magnesia, l*55=99-87,Varrentrapp), 

 while its hardness, 6, and absence of micaceous structure, render it entirely 

 distinct. It approaches scapolite in composition, but with a smaller quan- 

 tity of protoxide. I am led to allude to this species from the fact, that an 

 intelligent foreign mineralogist, to whom I showed some of the corundel- 

 lite, remarked that there appeared to be a similarity between the species. 

 There is however a most marked difference, in that corundellite is a mica. 



