The Mona Marble is a species of serpentine intermixed with white limestone: it has been already described ([132]).
SCOTTISH MARBLES.—Scotland affords many valuable and beautiful varieties of marble.
175. Tirie Marble.—Few of the British kinds of marble have been more admired than that obtained from Tirie, one of the Western Islands of Scotland. It is of a reddish, sometimes a delicate rose-coloured tint, and sometimes white; and is always intermixed with other minerals which add to its beauty. The most common of these is of black colour, and called hornblende; the others are pale green sahlite, blackish brown mica ([123]), and green chlorite. In some varieties the hornblende is more abundant than the marble.
176. Assynt Marble.—At Assynt, in Sutherland, a white marble has been discovered, which is perfectly solid and pure, and entirely free from blemishes or stains. Blocks or slabs of it may be cut of almost any size that can be required. This marble acquires a smooth surface, but remains of a dead hue; whence, of course, its uses as an ornamental marble are much circumscribed.
177. Isle of Sky Marble.—There is found in the Isle of Sky a marble of pure white colour, which appears capable of yielding large and valuable blocks. Its fracture is granular and splintery, and its texture fine. It is harder, heavier, and more compact than the marble of Carrara ([146]); and is apparently well fitted for all the purposes of sculpture. But it has the defect of being very unequally hard. While some parts of the stone are nearly as easy to work as that of Carrara, other parts are so hard as to add a charge of near fifty per cent. to the cost of the working.
178. Sutherland Marble.—Some beautiful specimens of marble of dark brown colour, veined with whitish, light red, or light brown, have lately been brought from the county of Sutherland. These appear of close texture, are susceptible of a beautiful polish, and are capable of being wrought into extremely beautiful slabs for chimney-pieces and other ornamental purposes.
179. Glen Tilt Marble is of white or grey colour, and veined or spotted with yellow or green; some specimens are nearly white. The granulations are peculiarly large; and, in its aspect and composition, the Glen Tilt has great general resemblance to the Pentelic marble ([143]). This marble has of late attracted the notice of the Duke of Athol, through the suggestion of Dr. Macculloch; and chimney-pieces of it have since been made. It is obtained from a valley of the same name in the county of Perth.
180. Blairgowrie Marble.—A few miles from Blairgowrie, in Perthshire, there is an excellent granulated broad-bedded marble, of sugar-loaf texture, and as white as the finest statuary marble. It may be easily raised in blocks and in slabs of great size, perfectly free from blemishes. This marble is supposed to be well adapted for ornamental architecture, but its large sparry texture renders it unfit for the sculptor.
181. Glenavon Marble is of white colour, with large granular concretions, somewhat like spangles, and as large as the scales of fishes. This is a valuable kind; but its situation in the forest of Glenavon, on the property of the Duke of Gordon, is remote and difficult of access.
182. Ballichulish Marble.—On the north side of the ferry of Ballichulish, in Lochaber, there is a rock of marble, of beautiful ash-grey colour, and of a fine, regular, and uniform grain, which is capable of being wrought into blocks or slabs of any size, and is susceptible of a fine polish. This marble is finely sprinkled throughout with grains and specks of pyrites ([236]), and with grains and specks of a beautiful lead ore, which to the eye appears to be rich in silver. If used for ornamental purposes, it would be a bright and beautiful metallic marble.