238 JOURNAL OF THE PLYMOUTH INSTITUTION. 
secondary origin of the schorl as a constituent of these rocks 
generally. We note this also in the occurrence of schorl-pseudo- 
morphs after felspar. 
Schorl-rock, or “ schorlite,” is properly a mixture of schorl and 
quartz, commonly found in nearly equal proportions. It has several 
forms of textural constitution, and at times is composed of frag- 
ments of massive schorl and quartz of considerable size, presenting 
a prominent black-brown and white variegation. It occurs in all 
gradations of structure between this coarse, irregular mixture, and 
a very fine-grained, highly-crystalline, dark-grey rock—as near 
Shaugh—which might be used for ornamental purposes with very 
good effect. Curious associations of schorl and quartz are likewise 
found segregated in the midst of the granite. A schorlaceous 
rock near Meavy display the proof of alteration in the existence 
of quartz-pseudomorphs after felspars. There are also some 
very curious brecciated schorl-rocks in the same locality ; and at 
Wigford, one with porphyritic quartz blebs and crystals. 
Luxulyanite.—The association of tourmaline with felspar under 
certain conditions produces a rock which is known, from the 
parish of Luxulyan, where it was first observed, as Luxulyanite. 
This is the rock of which the Duke of Wellington’s sarcophagus 
is made—a mixture of black or very dark greenish-black tour- 
maline with pink felspar. Though first to all appearance noted 
here by myself, Luxulyanite is by no means of infrequent occur- 
rence on Dartmoor. The normal form occurs at Leather Tor, 
also at Trowlesworthy; and I have found typical examples 
brought down by the Tavy as far as Denham Bridge. A very 
striking example is supplied by Lee Moor, in which the felspar 
is pure white. Near Chagford there is a fine-grained Luxulyanite 
plus a little mica, associated with a granite in which the mica has 
been replaced by schorl. I have also found this rock, with white 
felspars, near the Cheesewring. 
A rock closely allied to Luxulyanite occurs on Saddleback and 
near Shell Top—massive schorl with felspar crystals porphyriti- 
cally developed; sometimes small and irregular, sometimes of 
considerable size, and well formed. The schorl in what I regard 
as the leading variety forms a matrix. Quartz occasionally occurs. 
The felspar is at times pink, at others white, and sometimes has 
a yellow cast. 
