Prof. B. Silliman, Jr., on some American Minerals. 379 



■ VI .. . 



This analysis gives the ratio Si 4 A1«R* = R 3 Si + 3(Al 7 Zr) 2 Si. 



which gives the following result : 



4 atoms silica . . 2309 24 = pr. ct. 31-93 



6 " alumina . . 385400* " 53-30 

 3 " lime , . 106806= " 1477 



7231-30 100-00 



As however the mineral is hydrous and the analysis confessedly 

 only approximate, this formula cannot be regarded as entirely 

 correct, but it will be found useful in connexion with the results 

 which follow. 



The mineral which most closely approaches Smith's Emerylite 

 as far as our observations authorize us to form an opinion, is the 

 next in order and marked in our analyses " A. 57 



A. This mineral is from Village Green, in the town of Aston, 

 Chester Co., Pa., and was sent to me by Mr. L. White Williams, 

 of Westchester, to whom mineralogists are much indebted for 



t 



bringing to light many interesting things. It is associated with 

 corundum, and occurs in considerable masses, and so much re- 

 sembling common mica as to have escaped notice until Dr. 

 Smith's observations on " Emerylite" called my attention to the 

 minerals associated with the American corundums. Form like 

 mica, apparently hexagonal, folise easily separable but inelastic 

 and brittle. Color white, transparent in thin foliae. Lustre, sil- 

 very, vitreous and pearly. Hardness 3 5. Gravity 2 995. B. B. 

 in forceps exfoliates and emits a strong light, fuses on the edges of 

 thin laminae. In the close tube it is hydrous and gives very feeble 

 traces of fluorine. It behaved with the fluxes like the Turkish 

 mineral. A qualitative analysis showed the presence of silica, 

 alumina, lime, magnesia, soda, a trace of potash and iron, water, 

 and fluorine, the last in very feeble quantity. 



The quantitative analysis of this species is still incomplete in 

 its alkaline constituents, which are given by the difference, and 

 the amount of water is probably placed too high.* The analysis 

 ^vas conducted under my direction, by my pupil, Mr. Wm. J. 

 Crawe. Three analyses gave him as follows : 



I. II. III. Oxygen. 



Si 32-311 31060 31201 16-24= 4 



• • ■ 



A l 49-243 51199 51603 23-74 6 



Ca 10663 



Mg 298 -283 499 {■ 342 1 



NaandKf 2-215 



* 5 270 «-smn 6-270 4 *7' 2 * 



100 000 



9 239 



10146 



•283 



•499 



2-969 



1 22 1 



5 270 



5 -270 



100-000 



100000 







* The mean of two determinations. f By the difference 



