274 The American Geologist. April, 1893 
intergrowths of quartz and feldspar occur and these are supposed to be 
of secondary origin, as has been shown by Irving and Romberg to be 
sometimes the case. The author concludes that the above mentioned 
minerals of a porphyritic nature have been developed in an originally 
clastic rock as the result of orographic disturbance. Internal mechani- 
cal movement seems to have had little to do with their formation. "The 
development of the porphyritic constituents seems therefore to be due 
to a partial recrystallization of the rock as a result of what I would call 
static metamorphism — i. e., metamorphism in which pressure is the im- 
portant factor, in contrast to internal movement, though heat and a 
mineralizer were important adjuncts." 
Zur Genaucn Kenntnis der PJwnolithe dcs Hegaus. Von H, P. Gush- 
ing nnd E. Weinschenck, in Munchen. Phonolites and phonolite tuffs 
from Hohenttwiel, Gonnersbohl, Staufen, Hohenkriihen, Schwindel, 
Magdeberg, Duchtlinger Wald,Ploren and Eosenegg, in their petrograph- 
ical relations form the subject of this paper. The territory is a small 
one, making noteworthy the very variable character of the phonolites oc- 
curring therein. The different types found occurring were nosean phono- 
lite, noseanophyre, leucite phonolite, nephelite phonolite and trachytic 
phonolite. The nosean phonolite is characterized by porphyritic sanidine, 
hauyne and augite in a groundraass of sanidine, aegerite and nosean, 
with nephelite either absent or present in only small quantity. The 
noseanophyre ^from Magdeberg and Schwindel is noteworthy from 
the much less prominent porphyritic structure. Sanidine, occasional 
hauynes, and still rarer augites are the minerals of the first gener- 
ation. In the groundmass in addition to sanidine, aegerite and nosean, 
nephelite appears in its characteristic four or six sided sections as a 
characteristic constituent. On the small hill of Staufen two ex- 
tremely different phonolites occur, true leucite phonolite, and an or- 
dinary nephelite phonolite. In both porphyritic crystals of sanidine, 
hauyne and augite are of only occasional occurrence, and in both nosean 
does not appear in the groundmass. The first is characterized by 
abundance of small leucite crystals and non-appearance of nephelite; In 
the second no trace of leucite is found and nephelite is abundant. 
Finally from Gonnersbohl a last well-marked type is found marked off 
from the rest by the non-appearance of either leucite, nosean or nephe- 
lite in the groundmass, which has a trachytic structure; the needle 
shaped sanidine crystals show well marked flow structure, and between 
these the arrangement of the zeolite crystals makes it very probable 
that they arose from an original glassy base. In all these rocks apatite 
is abundant, titanite common and zircon occasional. Interesting is the 
occurrence of hauyne minerals in two generations, which Rosenbusch 
says does not happen.* Micro-chemical tests, wherever these minerals 
were fresh, showed that the porphyritic crystals were hauyne, those In 
the groundmass nosean. The latter were locally colored a beautiful 
deep blue, and this color is easily produced where not present, by simple 
*Rosenbuscli, Mikroscopischc Physiographic der massigen Gesteine, Stuttgart, 
1887, p. 614. 
