1893.] Mineralogy and Petrography. 1087 
MINERALOGY AND PETROGRAPHY. 
The Schists of Southern Berkshire, Massachusetts.— 
The sericite schists of southern Berkshire Co., Massachusetts, and 
northern Litchfield Co., Conn., contain phenocrysts of feldspar, garnet, 
staurolite, tourmaline, biotite, and ottrelite, imbedded in an aggregate 
of feldspar, quartz and sericite, which contains, besides the phenocrysts, 
a large number of metamorphic minerals. The large feldspars are 
often filled with secondary granophyre, and this mineral, the garnet 
and the tourmaline, are frequently built out by secondary enlarge- 
ments. The core of the feldspar is so often bounded by crystal out- 
lines that Hobbs’ regards the mineral as having resulted from the re- 
crystallization of the clastic grains of the original rock. The garnets, 
in addition to their peripheral enlargements, are often possessed of a 
rim of staurolite and magnetite crystals, supposed to be the product of 
reactionary action between the garnet and the surrounding minerals. 
The author believes the phenocrysts to have been developed by static 
metamorphism (simple pressing) from the constituents of a fragmental 
rock. 
The Phonolytes of the Hegau.—The phonolytic rocks of the 
Hegau, Eifel, Germany, so well-known because of the beauty of their 
hauyne constituents, have been subjected to a comparative study by 
Cushing and Weinschenk, who find them not all phonolites, as they 
have heretofore been regarded. The essential characteristic 
constituents of the group are sanidine, nosean, hauyne, nephel- 
l ine, leucite, augite and aegerine, and the accessories, biotite, apatite and 
son: All the rocks are more or less porphyritie, with sanidine and 
the members of the hauyne group in two generations. Of the latter 
the larger crystals and those of the first generation are hauyne; the 
smaller, those of the second generation, nosean. The former are always 
more or less altered into zeolites, while the latter are usually fresh. 
.. Contrary to the general statement made with regard to these two min- 
erals the hauyne is not always blue nor the nosean colorless, but 
rather is the opposite the case. An important discovery made during 
the investigation is to the effect that nepheline is by no means common 
X Edited by Dr. W. S. Bayley, Colby University, Waterville, Me. 
? Bull. Geol. Soc. Amer., Vol. IV, p. 167. 
3 Minn. u. Petrog. Mitth., XIII, p. 18 
