28 
PERMIAN BRECCIA OF LEICESTERSHIRE. 
Feb., 1892. 
to contain small grains of decomposed felspar and hornblende 
in a compact matrix. Probably a porpliyrite. Certainly not 
from the Charnwood series. (64.) A fairly angular frag¬ 
ment from Overseal, which does not appear as if it had 
travelled far. Examined microscopically, the ground mass 
is seen to consist of decomposed felspar, apparently plagio- 
clastic, a moderate amount of viridite, probably replacing 
augite, sometimes exhibiting an opliitic arrangement, and 
interstitial black and deep brown matter, which I think 
indicates the former existence of a basic glass. The rock is 
microporphyritic, the felspars being probably, at any rate in 
part, plagioclase; and it appears to have been rather vesicular, 
the cavities being now occupied by a chloritic mineral with 
a ringed or banded arrangement. Also there are several 
grains of a pinite-like mineral, more or less speckled with 
opacite, and with a rich brown dust. In several of them the 
exterior has a corroded aspect, as if the mineral had consoli¬ 
dated at an early period and had subsequently been attacked 
by the magma, but one or two have a prismatic form, with 
an occasional imperfect transverse cleavage. A basalt, though 
not one of the most basic. 
III. —Volcanic Grits and Agglomerates ; and Argillites. 
Probably from the Charnwood Series. 
(74.) An angular fragment, about 4in. x 2in. x 2in.,with 
edges slightly rounded, consisting of a piece of green argillite 
with an adherent volcanic matrix, the latter a good deal 
decomposed. This may be from one of the Charnwood 
breccias, which contain large argillite fragments. (20.) A 
subangular somewhat rounded specimen of a fairly coarse 
grit, consisting of fragments of lava, some of which are dis¬ 
tinctly andesitic in character, plagioclase microliths abounding. 
This rock and the one following are very probably from the 
Charnwood series. (30.) A fairly angular specimen of a 
coarse volcanic breccia composed of greenish-grey and 
darker fragments. (72, 108, 135.) Three specimens, two 
from Overseal, of fine-grained, greenish, speckled volcanic grit, 
one angular, the others somewhat rounded, one of them being 
striated ; all bear much resemblance to rocks of the Charn¬ 
wood series. (21.) An angular piece of a dull-coloured volcanic 
grit. Some of the fragments in it have indications of a slight 
fluidal structure. Epidote and secondary hornblende have 
formed, and there is a considerable amount of micro-mineralo- 
gical change. It contains the curious mineral described by 
me in 1891.* The specimen bears most resemblance to rocks 
* “ Quart. Journ. Geol. Soc.,” Yol. XLVII. (1891), p. 88. E. Hill 
and T. G. Bonuey, “ On the North-west Region of Charnwood Forest.” 
