

386 Prof. B. Silliman, Jr., on some American Minerals. 



It was fused with carb. potash and caustic potash, and its analy- 

 sis yielded 



i. ii. in. 



Silica, . . . 4092 40389 40-389 



Alumina, . . 5601 55729 56-618 



Magnesia, . . -28 -280 -280 



Water, . .3 09 1-840 2794 



100-90 98-238 100079 



♦ • • 



These analyses correspond closely with 8 Si 10 AI 3H. 



8 atoms silica = 4618-48 =perct. 40-59 



10 " alumina = 6423-30 M 5644 



3 " water = 33744 « 297 



11379-22 10000 



We have then the formula 



• •• ••• ■ • • 



8A1 Si+Al* H*. 

 The Worthite of Hess gave the formula 



*»« «*« S € | 



5A1 Si-f- Al H 3 corresponding to his analysis, viz. : 

 Silica, . ...... 



w • # 



Al 

 K 



Mg 



40-79 

 53 06 

 4-63 



0-88 



99-36 



Worth 



judging of the similarity of these two minerals in other respects. 

 The probability of being able to refer the present mineral to 

 kyanite seemed to me at first quite strong, but I was unable by 

 any care to procure an amount of silica less than that given in 

 these analyses. Should this mineral on further examination and 

 comparison prove to be distinct, I propose for it the name Monro- 

 lite, derived from the locality where it was found. 



* 



IV- On the identity of Sillimanite, Fibrolite and Buchol- 



zite with Kyanite. 



Sillimanite was originally described by Bowen * from an analy- 

 sis made in Yale College Laboratory in 1825 ; which showed it 

 to be a silicate of alumina with a proportion of silica too high to 

 allow it to come within the formula of kyanite. It was subse- 



Jour. Acad. Nat Sci., PhiL, iii, p. 375, 



