MINERAL PRODUCTS. 
161 
rocks, furnishing us with a probability only of being prolonged in one direction. At an uncer¬ 
tain interval it may appear again, as it were forced up through the other rocks, and attended 
uniformly with precisely the same conditions. In Williamstown, it apparently forms part of 
two interrupted ranges : one near the eastern base of the Taconic range ; the other, near or 
at the base of the Hoosic mountain range. Along the latter line, some of the heaviest masses 
of this rock appear; thus. Oak hill, between Adams and Williamstown, rises fifteen hundred 
feet, as already stated. In the east part of Bennington, in the same range north, is a much 
larger mountain ; and at the south in Dalton, at the Gulf, is another mountain of the same 
material. The western range, if one exists, is far less important: it is less in extent, and less 
regular in its appearance. 
Granular quartz is rarely if ever traversed by veins, except those of a siliceous kind. 
Disseminated in fine particles, we frequently meet with sulphuret of iron; in fact, a very 
large proportion of the rock is brown on the outside, from a stain derived from the decompo¬ 
sition of this substance near the surface. As a mining rock, it is of no importance ; but it is 
a valuable rock in itself, especially those parts of it which are granular, and those which are 
the least crystallized in the mass. This kind forms an excellent firestone, and is employed 
for furnace hearths. It is also a good building material, whenever it is sufficiently separated, 
or broken up in the mass in the direction of the layers and natural joints. The white granular 
or arenaceous variety is an excellent form of silex for crown glass, for sawing marble, sand 
paper, scouring, etc. The ordinary hard variety of quartz decomposes slowly. The region, 
however, in the neighborhood of this rock, is greatly infested with loose round fragments of 
the size of paving stones. In some places the soil is filled with them, and they are exceed¬ 
ingly troublesome in roads. In consequence, too, of its hardness, most of the boulders in the 
range of the Taconic system are of this rock. 
Mineral Products derived from the Slates and Limestones of the Taconic System. 
The most abundant product derived by decomposition from the slates and slaty limestones 
of this system of rocks, is hematitic iron, or limonite. The original state of this ore must 
have been partly that of an oxide disseminated in that part of the system where the limestone 
and slate come together. We often find talcose layers, yellow, ochrey, and white argillaceous 
matter commingled together in various states of change; some having become a perfectly 
soft or earthy stratum, and others harder and less changed, but still retaining some of the 
characters of the rock. From such a source, it is conceived the hematitic ore originated. 
After decomposition and disintegration, the earthy matter, charged with the oxide, accumulated 
in some partially closed valley, where it underwent a further change by a more perfect sepa¬ 
ration of the oxide. In process of time, the arrangement of the materials becomes as we now 
find them; the pure oxide in masses enveloped in an ochrey clay, with bands of white clay, 
which is one of the purest forms of this substance. A still farther change has sometimes 
taken place, by the conversion of the clay into gibbsite, which change is precisely analogous 
to what takes place in the conversion of the ochre into limonite. Intermixed with hematite 
Geol. 2d Dist. 21 
