Haworlh on the Arduean Geology of Missotirl. 389 
the c/dR and R faces well developed, as is shown in fig. i. 
The quartz grain is almost entirely surrounded by feldspar 
crystals. Such idiomorphic quartz is very important in consid- 
ering the structure of the granites. 
Another verv interesting feature of the quartz is the un- 
usually great abundance of fluid in- 
clusions. They vary from 0.025 
mm. in diameter to so small a size 
that they can scarcely be seen when 
magnified 300 diameters. Gas bub- 
bles are often present, but no one 
was observed which was in motion. 
Little cubic crystals— sodium chlo- 
ride? — were quite common in num- 
ber 332. 
Very frequently these fluid inclu- 
sions are arranged in lines approxi- 
mately parallel, and also are some- 
^d " f dlr^posiVVrKT^^^ times in planes cut by the section at 
ScSm,Xer.S'" ''™™ different angles. These recall the 
"solution planes" of Judd. 
It is very rare indeed to find anything at all resembling the 
hair-like inclusions so common in granitic quartz which Hawes* 
thought to be rutile needles. In a thin section made from a 
sandstone just north of Mine La Motte station, however, many 
such inclusions were seen. Now if the sandstone was formed from 
the disintegrated granites and porphyries near by, it is strange 
that the first section made from it would show more of these 
inclusions than can be seen in ncarlv two hundred sections of 
the granite and porphyrv. 
Orthoclasc. The orthoclase in nearl}- all thin sections exam- 
ined has a strong tendency to assume an idiomorphic sti-ucture. 
The faces oP, 00 P and P^ are frequently quite well devel- 
oped. It is not uncommon to find beautiful micropegmatite 
occuring in tJic same specimens with these idiomorphic crystals. 
The orthoclase is often quite badly decomposed, but the 
granites from the quarries are quite as fresh as the average 
Fig. 1. 
X 40 diameteii?. 
This shows an idioniorphie 
quartz in pranite, with R. and coR 
' Mineralogy and Lithiology of New Hampshire. 
