196 TRANSACTIONS OF THE ~ [APR Loy 
Felsite porphyry. Few phenocrysts, many characters of 
surface flows. This includes nearly all the acid effusives, and 
laps over on the one hand into quartz-porphyry and on the 
other into an acid porphyrite. 
B.—Basic Effusives. 
1. Diabase. This is the chief type. 
2. Feldspar-porphyrites, including a few basic lavas, strongly 
porphyritic, purplish in color. 
Dyke Rocks. Only basic dykes are known. 
1. Diorite-porphyrite and Camptonite. 
2. Diabase and various porphyrites. 
3. Augite-porphyrite. 
Sopa GRANITE. 
(JUARTZ—PORPHYRY. 
Two occurrences in the Quaco Hills, one on the Upper Quaco- 
Road, the other near Golden Grove, seem to merit special no- 
tice. The porphyry is even grained, compact and homogeneous, 
with abundant phenocrysts of quartz and orthoclase, the quartz 
predominating. No characters of surface flows were observed ; 
the rock appears not to grade into the felsites and ash-rocks in 
which it occurs, and may be in both cases an intrusive sill or a 
heavy dyke of post-Coldbrook age. It is very similar in character 
to the quartz-porphyry (is claystone- porphyry”), which occurs 
at the base of the Siluro-Devonian in Western St. John County 
(Dipper Harbor Road). 
Under the microscope this rock shows abundant quartz pheno- 
erysts, somewhat corroded at times, but usually with well marked 
erystal outlines. They show what seems to be a polysynthetic 
twinning, very fine and faintly marked, visible in sections ap- 
proximately basal. This may be the rhombohedral twinning 
mentioned by Prof. Rosenbusch * as occurring in quartz- 
porphyry. The orthoclase phenocrysts are rather less abun- 
dant than quartz; they are usually once twinned, and present 
no special feature worthy of note. Dark silicates are absent in 
the sections examined. Iron ores occur in scattered granules. 
The groundmass is microgranitic and of very even texture, com- 
posed of quartz and untwinned feldspar. 
The color of this rock in its freshest occurrence is a bright 
pinkish-red ; near Golden Grove it is pale green, weathering to: 
brown, and much altered. 
* Mikrosk. Phys. der Massigen Gesteine, p. 355. 
