STRUCTURE OF MAINE GRANITES. 25 
6. Quartz diorite, used for building purposes and not classed com- 
mercially as " black granite." This contains only lime-soda feld- 
spar, with quartz, hornblende, and biotite. 
The first three groups include nearly all the granite quarried in the 
State. Quartz monzonite is quarried at Sprucehead, Knox County, 
and at Norridgewock, Somerset County; hornblende granite is quar- 
ried in a small way on Mount Desert Island, and quartz diorite is 
quarried at Bryant Pond, Oxford County, and has been quarried at 
Hartland, Somerset County, and for local use at Alfred, York County. 
The general appearance and petrographic peculiarities of the stone 
at each quarry will be briefly stated in Part II, in the descriptions of 
the quarries and their products, and a classification of Maine granites 
based upon economic principles will be found on pages 72-75. 
Maine granites as exposed at the quarries show a wide range of 
texture. Some are porphyritic, others even grail ed, ranging from 
very fine, in which the size of the particles averages about one- 
fiftieth inch (one-half millimeter) to very coarse, in which the feld- 
spars measure an inch or more in diameter. They exhibit also con- 
siderable variety of color — pinkish, reddish, gray of various shades, 
and light lavender. The differences in the color of the two feld- 
spars and the variations in the amount of biotite and in the size of 
its scales produce more or less marked contrasts of color and of shade. 
The quartz also, if smoky, darkens the general color, and if clear, 
lightens it. 
GENERAL STRUCTURE. 
The term " structure " embraces all the divisional planes that trav- 
erse the rock. These occur at intervals ranging from a microscopic 
distance to one measured by scores of feet, and either cross or, very 
rarely, give a course to the texture resulting from crystallization. 
FLOW STRUCTURE. 
At some of the quarries (as Dodlin Hill, near Norridgewock, and 
Clinton Sherwood quarry, on Crotch Island) two varieties of granite 
lie in contact, the dividing line between them being vertical (see p. 
109 and figs. 18 and 32 for details) . One of the granites at Dodlin Hill 
also shows a light and dark vertical banding. The direction of the 
flow of the granite at these quarries must therefore have been vertical. 
At the Mount Waldo quarry, near Frankfort (see p. 154), vertical 
flow structure also occurs. At Tayntor & Company's quarry, near 
Hallowell (see p. 120), a faint vertical banding is visible in one of 
the walls, and a thin section of the rock shows a {parallelism of the 
biotite. The same parallelism is seen also at an old quarry near 
Brunswick (see p. 76). The arrangement of the mica in the granite 
at both places was doubtless governed by the direction of the flow of 
