HARKER : LAKE DISTRICT IGNEOUS ROCKS. 
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are microspherulitic ; some show partial replacement by 
secondary quartz. In places, and especially at Great Yarlside, 
nodular varieties occur, the nodules often being one or 
two inches in diameter and sometimes six inches. They 
represent large spherulites (and probably in some cases 
lithophyses), which have been greatly altered, the original 
structures being obscured or obliterated, and the spheru- 
lites partly or wholly replaced by quartz and other substances. 
In places there is a considerable thickness of tuffs and 
breccias at the base of the rhyolite group. These frag- 
mental accumulations are not all of acid composition, and 
they differ from the tuffs, &c., of the Sea wf ell group in 
containing sometimes a certain amount of detrital material, 
chiefly sand-grains ; while some beds again are calcareous 
tuffs. 
II.— Intrusive Rocks, Older Suite. 
The rocks included here are closely associated with the Volcanic 
Series, and probably belong to the same great period of igneous 
activity, though their intrusion succeeded the extrusion of the volcanic 
rocks. The age of the intrusions is, however, a matter of inference 
rather than demonstration, and much more information is desirable. 
It is at least certain that a considerable number of the rocks are 
older than the epoch of the principal crust-movements. 
{a) Granophyres. The Ennerdale and Buttermere granophyre, 
occupying a considerable area on the west side of the dis- 
trict, is a pink fine- textured rock with indistinct quartz- 
grains and crystals of felspar. Thin slices show it to consist 
mainly of micropegmatite. There are chloritic pseudomorphs 
after augite and biotite. A number of smaller intrusions 
of granophyre (most of them, if not all, augitic) occur in 
the district. Some, such as that of Blea Crag, Langstrath- 
dale, contain small garnets. The well-known Armboth 
and Helvellyn dykes, also garnetiferous in places, are micro- 
spherulitic rocks, with porphyritic crystals of quartz and 
felspar which serve as nuclei for the spherulitic growths. 
