698 HENRY S. WASHINGTON 
this connection: SiO,=73.1, Na,O=2.5, K,L0=5.0. This rock 
from the Polveriera shows about the same amounts of silica and 
potash as that from the Cuddia Nera, but soda is somewhat lower, 
though in both the percentage of potash is greater than that of 
soda, and molecularly they are present in about equal amount. 
The distinctly high potash is noted by Foerstner as a character of 
the rock type. . 
Norm.—The norm of the Cuddia Nera rock is as follows: 
Norm 
OE Rely, sida et cee angen th cea atte eee ee ot LAGU re age Bitoaws 
(Oh cay eesnarteaa Winer ebana ae cs ena er tae RRS a ca kt tte 20.47 
Ha OR) ert Her AM a teats uh cA PAIRS ORS REINS Se on iE RL 22.01 
Nee pace ees tet lets oe ratte ins Ca ener Se ARE Q. 24 
INES ie Sep occat ke eae IR ike oe ne eet ee Raat re ee TE, ©) 
| Dee eats eet nse mele eee ted ural ol pe tater nd Ny bane bit 2S] 
Eby ic Rie nsec ed pec age es oe eked 0. 46 
LE aeeee ere PL lame Merle: Ona MRE Ponsa mii ch aes. ei de i, DD 
FA eRe la sald teal orleans So eti hT crt eae « gene oe pomMarceemeae 0.34 
97-55 
N RCI) see MORES PTT SM ta eagle ego te OAK ty eis. ks 2.24 
99.74 
The type falls within the dosalane class but is transitional to 
persalane, and is nearly on the border of order 3. The rang is 
decisively peralkalic, no salic lime being present, since acmite 
exists in the norm, and the subrang is also clearly sodipotassic. 
It is therefore in (I)IT, (3)4.1.3, so that the type should be called 
a varingose-grorudose. It will be seen that acmite constitutes the 
greater part of the femic minerals, and the presence of sodium 
metasilicate in small amount is to be noted as this is character- 
istic of the pantellerites, being correlated in the mode with the 
presence of cossyrite. 
Mode.—Through the presence of the hornblende the mode is 
somewhat abnormative. From recalculation of the norm and 
study of the thin sections it may be expressed approximately 
as follows, the cossyrite being assumed to have the composition of 
that analyzed by Dittrich" 
t J. Soellner, Zeits. Kryst., XLVI (1909), 540. 
