266 
Buell—Geology of the Waterloo Quartzite Area. 
LITHOLOGICAL CHARACTERS OF THE QUARTZITES. 
Prevailing Characters —The sharp folding of the strata indi¬ 
cated by the record of dips and strikes, is accompanied by evi¬ 
dences of extreme metamorphism. This is apparent in the 
ledge surfaces in the abundance of seams and cracks, and in the 
ease with which all angular surfaces are chipped under the 
hammer. Its effects are also shown on close examination of 
the rock texture. As compared with the usual quartzite rock 
from the Lake Superior Huronian it shows a much less distinctly 
granular appearance. Outlines of individual crystals are very 
indistinct and in the coarser textured rock ill-defined mottlings 
take their place. 
The usual fresh aspect of quartzite exposures charac¬ 
terizes both the ledge surfaces and in general the material 
forming the bowlder trains. But in the considerable talus ac¬ 
cumulations which lie on the margin of the Portland area many 
of the blocks are deeply exfoliated and similar evidences of at¬ 
mospheric action occur in some of the imbedded blocks of the 
Paleozoic. conglomerate that borders the same area. These 
effects are apparently due to the much greater time that these 
surfaces have been exposed than the glacially abraded ledges. 
The minerals recognized in these quartzites are few in num¬ 
ber, namely quartz with its inclusions of small crystals of zircon 
and magnetite, and fluid cavities, sericite and iron oxides. 
Variations in the size of quartz grains and their granu¬ 
lation from shearing, and in the amount of sericite 
present, have produced a somewhat wide range in the 
appearance of the material from the different parts of the field. 
The grouping of outcrops into isolated areas has given us, how¬ 
ever, a basis for the classification of these naturally blending 
forms, which will be followed in the descriptions of the princi¬ 
pal types. 
The Portland Type —The outcrops comprising this area afford 
the widest range in microscopic appearance. The rock is com¬ 
monly a coarsely crystalline quartzite with a somewhat mottled 
surface and splintery fracture. The secondary material is 
chiefly sericite and is relatively large in amount, often in suf- 
