216 
PETROLOGY OF LOCAL PEBBLES. 
Sep., 1889. 
The rock is exactly the representative of some of the 
rocks from Sutherland, with which Dr. Lapwortli made us 
familiar some years ago ; but the fact of its being made out 
of a tolerably pure quartz grit produces, of course, a differ¬ 
ence in its appearance from the absence of felspar and 
hornblende, which are present in the crushed gneisses of the 
north. 
(7) A yellow quartzite (9) from Sutton. 
This is an example of a rock that has been still further 
crushed and spread out than the last. The larger pieces 
forming the “eyes” are in many cases quite broken up, 
although the pieces are not moved away from each other or 
only slightly so, and the whole has been cemented into an 
exceedingly compact mass by abundant quartz, with mica 
flakes, in just the same way as in the last example. 
(8) A dark-reddish, laminated pebble (22) from Alvechurch. 
Exactly similar stones occur at Sutton. 
In this rock the crushing and rolling has gone still further 
than in the previous case. With the exception of a few 
opaque spots which seem to have determined the formation of 
many cracks, which have afterwards been filled or partially 
so with oxide of iron, I can distinguish no mineral but quartz, 
much of it in intricately interlocked grains. The whole rock 
has a good deal of dusty matter distributed through it, usually 
without any definite arrangement into lines. At most it is 
slightly heaped together in a few places. 
A pebble (38) from Sidnal presents some peculiar features. 
It has the look of a laminated mass of somewhat opaque 
grains separated by pale yellow lines, which occasionally show 
themselves as flakes of golden mica. The crumbly nature of 
the rock makes a good section difficult to obtain, and what I 
have got is not in the best direction for examining the speci¬ 
men. The grains are quartz, but a good deal crushed, and the 
cementing quartz has the interlocking texture A few frag¬ 
ments of felspar are suggested more than certainly recognisable. 
The main points in which the quartzites which I have 
mentioned differ from those of the Lickey. of the Nuneaton - 
Hartshill ridge, and of the Wrekin, so far as they are known 
to me, are 
(a) The original quartz grains are very much less perfectly 
rounded. 
(b) The average size is much less. 
(c) The quantity of zircons and other heavy minerals is 
much greater. 
