Augen Gneiss and Moine Sediments of Ross-shire. 341 
(such as andalusite) and no hornfels structures. Recrystallization and 
the development of foliation have converted them into schists and 
gneisses, typical products of regional metamorphism. 
But in certain areas around the edge of the granite, in a strip of 
country that varies in width up to about a mile, quite other types of 
rock are found. Many of them are fine-grained, flinty-looking, with 
a well-marked banding due to bedding. From the abundance of black 
mica in very small plates these rocks have a bluish leaden colour. 
They are hard and splintery, breaking in any direction, and sometimes 
contain rounded garnets as large as peas, or prisms of andalusite half 
an inch in length. When first they were encountered these rocks 
were recognized by Dr. Peach as hornfelses, typical thermo-metamorphic 
products of the action of the granite intrusion on sandy shales. 
Nothing like them had been previously seen in any part of the Moine 
country. 
In the rocks of the Southern Highlands, however, various instances 
are known where hornfelses retain in exceptional perfection the original 
characters of sedimentary rocks. On the north-west of the Ben 
Vuroch augen gneiss (a foliated granite by no means unlike that of 
Carn Chuinneag) Mr. Barrow had previously detected pyroxene 
hornfelses (cale-flintas), fine-grained, with bedding preserved. Near 
Loch Awe and in Knapdale and Islay thin bands of hornfels have 
been frequently observed at the margins of epidiorites that were once 
intrusive dolerites. 
The minetals of the banded hornfelses are quartz, felspar and brown 
mica. Very generally they contain garnet, and sillimanite also is 
common as small prisms densely clustered. Pseudomorphs of andalusite 
are found only along certain bands, sometimes in the form of typical 
chiastolite with the black cross-shaped markings, sometimes in large 
eumorphic prisms; but the mineral is always replaced by white mica 
and kyanite. Pseudomorphs after cordierite have been seen in one or 
two rocks, and there are also compact pyroxene hornfelses derived 
from the marl-bands (calcareous shales) that give rise to the zoisite 
hornblende granulites under other conditions. The fine biotite hornfels 
is often ‘spotted’ with small spots, exactly in the same manner as 
a spotted slate from the aureole of a Cornish granite. 
The banding of the hornfels is due to the alternation of lamine rich 
in quartz with others more rich in biotite. The quartzose bands often 
contain minute pebbles of rounded quartz; sometimes they have the 
structure of argillaceous sandstones, well preserved in every detail. 
On the surfaces of certain layers there are markings strongly suggestive 
of sun-cracks and ripple-marks, and others which may possibly represent 
worm-tubes. The banding is evidently due to bedding, and the rocks 
were originally fine laminated arenaceous shales. This has been con- 
firmed also by chemical analyses. Where the contact alteration is most 
intense or the rock has been very argillaceous the clastic structures, 
as might be expected, are less obvious, but they are never absent. 
It is to be noted that in the least sheared hornfels the bedding is 
generally lying at gentle angles, and over wide areas near Kildermorie 
and south of Loch Chaoruinn it is dipping at right angles to the 
general direction of the bedding and foliation in the neighbouring 
