68 BRITISH PORPHYRIES. felspar and quartz, sometimes schorl, and rarely mica. One of the most remarkable examples is the schorla- ceous porphyry from Luxullian, in Cornwall; con sisting of black schorl and a little felspar and quartz as a base, in which are distributed large crystals of red orthoclase felspar. The sarcophagus for the late Duke of Wellington, now in St. Paul’s, is formed of one huge mass of this rock, which has received the name of Luxullianite. 1 A handsome porphyry, suitable for polishing, may be obtained from Tremore, near Bodmin. It occurs as a dyke, extending in an easterly direction from this place to the south of Withiel and St. Wenn. The rock varies in colour, but those portions having a reddish or flesh-coloured base, with crystals of white felspar, and occasionally some schorl and quartz, are the most beautiful, and occur in large quantity at Tremore village, and in a ravine above Ruthan bridge. This porphyry has been cut and polished by water power at Fowey Consols Mine, for private use; and it has a very handsome appearance, with the ad ditional advantage of being capable of extraction from the quarry in large blocks. Another variety from the same neighbourhood is composed of light pink crystals of felspar, with others of quartz and schorl, in a brownish-red felspathic base ; and a third (but apparently only occurring in small quantity) is 1 Mr. R. Hunt, Descrip. Guide Mus. Prac. Geol. p. 20.