THE HIGHLAND BORDER ROCKS OF THE ABERFOYLE DISTRICT. 
197 
confess that, while it is difficult to explain that association as a mere accident, 
they have not been able to establish definitely that the one series is the plutonic 
representation of the other, and they regard the question as an open one. The 
occurrence of albite gabbros in the above complex seems to us to go far towards 
proving that in the Aberfoyle area at least the coarsely crystalline rocks are comag- 
matic with the albite diabase and spilites. 
IX. The Hornblende-Schist Complex and Associated Sediments. 
A belt of metamorphic rocks has been traced from G-ualann north-eastwards to a 
point opposite the south-west end of the Drum of Clashmore, a distance of about 
2j miles. It is bounded on the south by a fault which is probably a branch of the 
Highland Fault, and a line of dislocation separates it from the unaltered igneous 
and sedimentary rocks to the north. The belt consists mainly of metamorphosed 
igneous rocks, chiefly hornblende and chlorite schists, but schists of sedimentary 
origin are found along the northern margin and also intercalated with those of 
igneous types. Their highly foliated character distinguishes the metamorphic rocks 
clearly from the unaltered rocks to north and south. The direction of the general 
strike of the foliation is north-east and south-west, and the foliation planes dip at 
high angles towards the north-west. 
Schists of Igneous Origin. 
Eastwards from the most easterly tributary of the Corrie Burn the schists are 
very uniform in character. The dominant type is a well - foliated crystalline 
hornblende schist, usually flaggy in character, dark green in colour, with a beautiful 
silky lustre, and sometimes veined with yellow epidote. The minerals entering into 
the composition of these rocks are mainly hornblende, albite, and epidote. Accessory 
minerals include zoisite, sphene, and apatite ; secondary chlorite, quartz, and 
carbonates occasionally make their appearance. 
The typical hornblende schists over most of that area are medium to fine-grained 
in texture, and show a well-marked linear foliation. The dominating constituent 
is hornblende in elongated crystals, euhedral in the prism zone but with irregular 
terminations, and showing pleochroism in pale greenish-yellow (X), olive-green (Y), 
and blue-green (Z) tints. It is accompanied by albite in more or less equidimen- 
sional grains along with a varying amount of epidote and accessory constituents. 
The felspar is rarely distributed uniformly. More usually it occurs alone or in 
association with epidote in rather persistent bands parallel to the foliation planes. 
In the medium-grained varieties, for example opposite Maol Ruadh, those bands 
swell out to form lenticles conspicuous in hand specimens. The latter represent 
perhaps large crystals or groups of crystals of the felspar of an original gabbro or 
coarse diabase, and their occurrence suggests that the rock had been consolidated 
prior to its conversion into a schist. The elongated hornblende crystals (see Plate III, 
