We pass now along the edge of the cliffs northward; these are not seldom so precipitous as to make a close examination impossible. The serpentine varies in character, being sometimes dull and compact, sometimes redder in colour, and containing larger bronzite crystals. The headland called the Horse is remarkable for the boldness of the jagged rocks that form its crest, which in form, colour, and even in aspect, recall memories of the gabbro of the Cuchullin Hills; the rock, however, is an ordinary serpentine.
Nearly a mile in a direct line north-west from Kynance is a cove called Gue Graze. A gully on the north side exhibits a granite vein; it resembles that already seen[1]. On descending to the beach we find the serpentine is in places much brecciated and cemented by steatite, which is here abundant. Much of the serpentine on the beach is rather peculiar in appearance (no. 5), being of a dull red colour, with obscure dark greenish lines, a slightly rougher fracture, and (under the lens) more granular texture than common; it is also remarkable for hardness and the absence of conspicuous bronzite. In many places it is sand-polished. The joints are often coated, as usual, with films of green steatite.
Returning to the higher ground and passing Vellan Head, we continue to observe the apparently stratified structure in the serpentine, which sometimes even seems to mimic current-bedding. Near the Head its dip is fairly persistent, about 50° south; but this does not continue for long; I observed, however, that it was often parallel to one of the leading systems of joints; and hereabouts fairly defined tabular jointing is not unusual. The end of the serpentine is reached at a spot called Ugethawr, on one side of George's Cove, to the south of the place where a well-marked valley descends to the sea; thus the breadth of this practically uninterrupted tract of serpentine, measured in a straight line from sea to sea, is about 214 miles. I could not find the actual junction of the hornblende schist and serpentine on the rocky slope; but it is possible to scramble down to the water's edge, and there it can be discovered in a little sea-cave. It is in many respects an interesting one. The hornblende schist is rather compact and very dark; so also is the serpentine, especially near the junction—so compact, dark, and hard[2], indeed, and with so conchoidal a fracture, that at first sight it might readily be mistaken for Lydian stone; it overlies the hornblende schist, which here dips rather evenly about 60° W.N.W., and seems to be closely welded to it. One or two thin tongues of serpentine are thrust into the schist within a foot or two of the junction. The serpentine is therefore
- ↑ The granite of Gue Graze may be regarded as fairly typical of the veins on the west coast; so that it is the only one which I have examined microscopically. It consists of quartz and felspar, both orthoclase and plagioclase. There is a scale or two of magnesia mica, a good many small clusters of minute granules of magnetite, with some fine needles and asbestiform fibres, some of which I think are tourmaline. There is an orthorhombic mineral of secondary origin here and there in the felspar, probably prehnite. One rather abundant microlith seems to be apatite; but there is probably another mineral also present. Altogether there are a good many included microliths and some minute cavities.
- ↑ Its hardness varies slightly, but is about 5.
