AUGITE-SYENITE AND GRANITELL. 115 
different directions, viz: toward orthoclase-gabbro and the non-quartziferous 
porphyries on the one hand, and toward granite and the quartziferous 
porphyries on the other. 
I have been somewhat at loss for a name for these rocks. In 1878 
Pumpelly designated as ‘granitic porphyry” one or two specimens of a 
red rock, sent him by the Wisconsin Survey, but according to Rosen- 
busch and the accepted nomenclature generally, a granitic porphyry is a 
rock witha finely crystalline admixture of the usual granitic minerals—quartz, 
orthoclase, plagioclase and mica or hornblende—with porphyritically devel- 
oped feldspar and quartz, and thus stands between the true granites and 
the felsitic porphyries. But all of the rocks under consideration in which the 
quartz is wholly secondary are essentially, or were, before the deposition of 
the secondary quartz, aggregates of feldspar crystals, with the orthoclase pre- 
dominating. The altered augite is the only other ingredient worthy of any 
consideration in determining on a name for these rocks, while it is always 
so subordinate as to be hardly more than an accessory, and from about a 
third of the sections is entirely absent. Regarding it as an essential ingre- 
dient, and the quartz in most cases as a secondary product, resulting from 
the leaching of the original feldspar mass, these rocks are nearer to the 
‘‘augite-syenite” of Rosenbusch than to any other previously described 
species among the pre-Tertiary rocks. The kinds in which the quartz is 
possibly primary would be then “augite-granite” or “granitell,” but no ex- 
act provision is made for these rocks in any system of nomenclature.’ 
As typical instances of the occurrence of these rocks may be men- 
tioned the pebbles of a conglomerate at the south foot of Mount Bohemia, 
Keweenaw Point, apparently included in the Eastern Sandstone; the irreg- 
ular masses apparently intersecting the orthoclase-gabbro of Mount Bohe- 
mia itself; many pebbles of the conglomerate at Eagle River, Keweenaw 
Point, where are found both fine-grained and coarse granite-like kinds; the 
prevailing pebbles of the Albany and Boston conglomerate near Portage 
Lake; the irregular masses intersecting coarse olivine-gabbro at a number 
of points in the gabbro belt of the Bad River region of Wisconsin ;? the 
'“Granulite” of Rosenbusch is without plagioclase, or the term might be used for the kinds almost 
free from augitic ingredient, and rich in large quartzes, 
See Plate XXII of this voiume, and also Geology of Wisconsin, Vol. III, pp. 45, 195. 
