68 
AMERICAN GEOLOGY. 
than it usually is. It is also the repository of many minerals. 
The peroxide of iron, barytes, strontian, carbonate of stron- 
tian, albite, pyroxene, hornblende, fluorspar, and sulphurets of 
iron and copper belong to this rock. It should be stated that 
the rock decomposes readily, and where exposed upon the lake 
or river shore, becomes cavernous. The ores and minerals 
occur in nests and strings, which run out, and hence has ever 
proved an unsafe rock in mining. The most common variety 
of granite occurring in the low ranges of the Blue ridge is 
composed of feldspar and quartz. It is always in irregular 
veins, and is sometimes auriferous. In other respects it is bar- 
ren of minerals, and in decomposition forms a porcelain clay. 
It is common in Guilford, Davidson, Cabarros, Mecklenburg, 
and Rowan counties, in North Carolina, and is associated with 
greenstone in dykes. A similar granite occurs in Macon and 
Cherokee counties. It is not uncommon in the Nantahala 
range, a spur of the Blue ridge. 
§ 56. Granites of the JVew England states. In Vermont, 
granite occupies a portion of the eastern slope of the Hoosick 
Mountain range. It does not appear in the western part of the 
range, but comes in east of Montpelier. 
Maine furnishes, however, some of the finest fields of archi¬ 
tectural granite.* It is light gray, of fine texture, and works 
easily. Columns from thirty to fifty feet in length may some- 
times be split out from the quarry. The granite of Hallo well 
lies in sheets or thick laminae, which may be reduced to 
columns by splitting in lines parallel with the grain of the 
rock. These granitic beds may be said to be sheeted, in con¬ 
sequence of the easy and ready cleavage of the mass on a large 
scale. Indeed, it is a spontaneous • separation into laminae, 
varying in thickness from one to three feet. It is not well 
determined how the granite received this peculiar structure. 
It is probable, however,-that it owes its sheeted structure to 
its flow at the time of its eruption, and the consequent cooling 
* Jackson’s Maine Reports. 
