

306 PROFESSOR HEDDLE ON THE MINERALOGY OF SCOTLAND. 
folds, convoluted and contorted in the extreme. This gneiss is composed of 
orthoclase of a somewhat bluish tint, passing occasionally to cream colour, and 
containing over half a per cent. of lime, a black or bronzy mica, probably 
lepidomelane, and pale blue quartz. This rock, which is highly characteristic 
from the manner in which its dark micaceous layers display the marvellous 
plications into which it has been crumpled, dominates throughout the county 
of Aberdeen to a much greater extent than the granite-blotched geological 
maps admit. 
In no place perhaps can the gneiss be seen actually abutting upon the 
quartzite, for there intervenes a bed, or a series of beds of limestone, associated 
for the most part with serpentine and with diorite. 
It has been stated above that the dip of-the quartzite was not absolutely 
conformable with that of the mica state—the relations of this quartzite have 
yet to be thoroughly investigated ; possibly it may prove to be the lowest 
member of the series; it is in the north somewhat talcose, and micaceous 
in its southern reaches. 
Such being the general relationships of the rocks—so far as regards the 
included limestones—their geographical position has now to be pointed out. 
The argillaceous mica schist is first seen in the north a few miles south of 
Cullen, in Banffshire: stretching thence to the S.W. it occupies the whole 
of the low ground of the vale of Deskford, Glen Isla, Glen Rinnes, Glen Livat, 
the Braes of Abernethy, and the upper reaches of Strath Alnack. The lower 
part of these hollows is occupied by a frequently interrupted, but on the whole 
very persistent bed of limestone. The general character of both schist and 
limestone is an absence of disturbance, trouble, folding, or dislocation of their 
beds. 
Of the quartzite little need be said: a considerable though detached mass 
of it appears in the neighbourhood of Cullen; the portion usually supposed to 
overlie the argillaceous schist of the western valley commences in the Durn 
Hill, south of Portsoy, and stretches in two parallel ranges of highly elevated 
land, protruding as it were through the sea of micaceous mud which lies at 
their feet, with but few breaks in the continuity of their course, till, converging 
after forming the buttressed walls of Glen Clunie, and sweeping westward 
along the ridge of Cairn Geodeh (Gey), they constitute the great masses of 
Ben Uran and Ben-y-Gloe. This quartzite reappears in small amount here and 
again, but is finally denuded off after forming the terminal 50 feet of the sharp 
summit of Aonach Beg, near Loch Ousan. 
Immediately above the quartzite there comes in a series of beds of serpen- 
tine, of at least three varieties, which alternate with limestones. These lime- 
stones are of so trifling and irregular a character as to lead to the suspicion that 
they are not sedimentary limestones, but are a product of the metamorphism 

