268 Buell—Geology of the Waterloo Quartzite Area. 
smaller quartz grains. Sericite forms but a small part of the 
interstitial material, being confined to isolated knots and streaks. 
The finely granulated quartz is abundant about the larger 
grains and stainings of ferrite are seen chiefly in association 
with the sericite. Undulatory extinction is common in the larger 
quartz sections (Plate VIII, Fig. .3). The layers in the Lake 
Mills outcrop belong to the Hubbellton type and exhibit unim¬ 
portant modifications. The prevailing color is a darker blue 
and the banding in some layers is more distinct. In other 
layers an increase of iron oxide produces an opaque black rock. 
Quartz individuals appear in the section to be of somewhat 
larger size with less amount of fine interstitial material. Iron 
oxide is present in larger quantity but sericite bears about the 
same proportion to the other minerals as in the Hubbellton 
sections (Plate VIII, Fig. 4). The black layers appear to be 
composed of very finely pulverized quartz, cemented by an 
opaque matrix in which magnetite composes a considerable 
proportion of the whole. 
The Red Quartzite .—This type has already been noted as 
present in considerable quantity on the surface of a drift ridge- 
midway between the Portland and the Hubbellton areas. It is 
a fine textured rock of pinkish gray color, of low translucence 
and presents on fractured surfaces a granular or saccharoidal 
aspect. Quartz individuals as seen in section are very small, 
usually not exceeding one-fifth of a millimeter in diameter. 
They are distributed quite uniformly through the section, and 
are enveloped in a comparatively large amount of sericite-bear- 
ing interstitial material. In one of the sections examined clus¬ 
ters of larger grains occur, in which the correspondence of out¬ 
line and slight orientation of axes indicate that they are 
simply the slightly displaced fragments of single crushed indi¬ 
viduals. (Plate VIII, Fig. 2; Plate IX, Fig. 2.) This rock 
resembles in composition and structure the Portland type, but 
in general appearance is very similar to the rocks of the Hub- 
bleton area. Its interest aside from its unknown derivation 
consists in its well defined red color and the consequent ease 
with which its bowlder distribution has been made out. Errat- 
