DESCRIPTION OF ROCKS AND ANALYSES 33 
G.Friedel,'! and for which kind of nephelite Morozevicz? proposed 
the formula K,Na,Al,Si,O,,, gives 32.4 °/o of it, but displaces the 
proportion of augite to olivine in favour of the former (45.48 °/o and 
8.03 °/o), thus giving discrepancies both with the eyepiece estimation 
and between the specific gravity determined and calculated (lowering 
the latter). For calculation of specific Srey served the main values 
given by Rosenbusch.? 
The figures of chemical composition of the augite calculated (sub 1, 
below) in the manner indicated above differ from a usual pyroxen 
composition in high lime content exceeding the sum of MgO-+ FeO, 
yet a comparison with augites from analogous rocks rich in lime 
and soda, as p. ex. the basalt of Rhön (anal. 3),* or in lime and 
potash, as p. ex. the madupite of Pilot Butte, Wyoming (anal. 2),° 
as tabulated below, shows some common features: — 
| | 
SiO, | 5220 | 50.86 AB 
| Al,O, we | 4.52 
LURLSAON 7.9 | Tas | 6.54 
| FeO | 6.06 | 1.82. | 3.26 
MgO | 6.96 lf DE 12.01 
| CaO I SOS sa Dal 101.81 | 
 Na.O 3.00 0.76 | 0.80 
| K,O = 0.42 | 0.36 
lag OM SE! 0.31 0.11 
| TiO, — I 3.03 1.44 
| P,O, | Tras | war 0.36 
| MnO | 0.54 | — -— 
| | 100.0 | 9916 | 100.35 
Spec. gr. 3.4 | =| 3.402 
1 Ch. et G. Friedel, Action des alcalis et des silicates alcalins sur le mica: 
production de la nepheline etc. Bull. Soc. Fr. Min. /3. 1890 p. 131. 
2 J. Morozevicz, Über die chemische Zusammensetzung des Nephelins. Bull. 
Acad. Sc. Cracovie, Cl. Sc. math. et nat. Octobre 1907, p. 992. 
3 H. Rosenbusch, Mikroskopische Physiographie I. 2. 4th. ed. 1904. 
* X. Galkin, Chemische Untersuchung einiger Hornblenden u. Augite etc. N. 
Jahrb. für Min., Beil.-Bd. 29. 1910. p. 681. 
5 Whitman Cross, Igneous rocks in Wyoming. Amer. Journ. Sc. 4. 1897. p. 130, 
W. F. Hillebrand, analyst. 
