WARREN COUNTY. 
173 
Granite. 
The most important mass under this head, is in Athol, at the base and in the vicinity of 
Crane’s mountain. It is white, tolerably coarse, and contains but a small proportion of mica. 
The feldspar decomposes rapidly, and forms that important material called porcelain clay. A 
very large proportion of the bed is in a crumbly decomposing state. The precise extent of 
this kind of granite has not been ascertained; it is, however, known to continue with little 
interruption for nearly twenty miles. The importance of this rock is derived wholly from its 
nature, and its ready conversion into clay. I shall therefore speak more of this product of 
the rock, than of the rock itself. 
The characters which predominate in all granites which furnish this material for the finest 
kind of pottery, are coarseness, with large plates of mica if any exists in the rock, and a 
white flaky talc, which perhaps appears only as a coating to the feldspar. A great length of 
time is required for the production of the clay ; for the changes which the materials pass 
through are slow and gradual, and are effected by slow molecular attraction, which in the 
first place dissolves the tie that holds the mass together, and is preparatory to those nicer 
changes by which the potash is liberated from the feldspar, and the silex and alumine in¬ 
timately blended in a soft snow-white mixture. Feldspar, which furnishes the clay, is 
composed of silex 64, alumine 20, potash 14, lime 2, or sometimes only a trace of the last 
substance. It is to the large quantity of potash that we are to attribute those changes which 
result in the formation of porcelain clay. The beds are not composed, as we should expect, 
of one homogeneous mass, but consist of layers of different colors; white, yellow and red 
predominating. Sometitnes the distribution into layers is imperfect, and the white and valu¬ 
able portion occurs in masses. In addition to the colored clays, the beds contain particles of 
quartz, nodules of manganese, and, what are quite interesting, large nodular masses of silex, 
of a secondary formation. 
It will be observed from these facts, that the changes are of an interesting as well as of a 
complicated character. It will be useful to occupy a moment in an exposition of these 
changes, and the sequence in which they occur. We must first state one or two facts in rela¬ 
tion to the solubility of silex. This substance, as it exists in rock crystal, when pulverized 
to a dust as fine as possible, is extremely insoluble by all the ordinary agencies. By means 
of potash or either of the alkalies, aided by heat, it is rendered highly soluble ; and while in 
this combination, weak muriatic acid, or even ■water, is also capable of holding it in solution. 
Silex is also contained in thermal waters; and when these are exposed to the air, and lose 
their temperature, the silex is deposited or precipitated in the form of a tough porous rock, 
around the places where the springs issue. In the formation of porcelain clay, which con¬ 
sists of alumine and silex, there is a loss simply of the potash ; the production of which may 
be accounted for by a solution of the whole or part of the potash by the water. But to account 
for the regeneration of silex in a solid concretionary state, and even its crystallization as is 
found to be the case in the interior of these nodules, is not so easy a matter; for we cannot 
