Parr IL § vi] CRYSTALLINE ROCKS—MASSIVE. 133 
many ordinary granites. Here and there an example may be found 
of a granite becoming fine-grained but containing large scattered 
felspar crystals. Such arock may be termed a porphyritie granite, or, 
if the ground mass be finely crystalline and tolerably uniform in 
texture, Granite-porphyry.' One of the most interesting structural 

Fig. 21.—VeEIn oF FINER GRAIN TRAVERSING A COARSELY CRYSTALLINE GRANITE. 
varieties is that termed graphic granite. It is distinguished by the 
manner in which the quartz has assumed the shape of long imperfect 
columnar shells, placed parallel to each other and enclosed within the 
orthoclase, so that a transverse section bears some resemblance to 
Hebrew writing. The two minerals have crystallised together and 
this has taken place in veins. The parallelism of the quartz shells 
seems to show that there could have been little or no internal 
movement of these veins when the component minerals assumed their 
crystalline forms. Some granites abound in enclosed crystalline con- 
eretions or fragments. These are sometimes mere segregations of 
the materials of the granite, when they are usually ovoid in form and 
porphyritic in structure; in other cases they are fragments of other 
rocks, and are then commonly schistose in structure and irregular 
in form. In the centre as well as round the edges of large 
bosses of granite the minerals occasionally assume a more or less 
' On granite porphyry see Zirkel, Microscop. Petrog. p. 60. Kalkowsky, Neues 
Jahrb. 1878, p. 276. 2 J. A. Phillips, Q. J. Geol. Soc. xxxvi. p. 1. 
