80 
STOCKBR1DGE LIMESTONE. 
MINERAL CONTENTS. 
The mineral beds or veins in the Stockbridge limestone are few, and of little importance. 
Copper and iron pyrites, sulphuret of lead in small lumps and particles, and silver in some 
form and condition, have been long known at Singsing. The vein containing the silver 
has not heen opened since the war of Independence. 
This rock, however, contains a large amount of oxide of iron, disseminated principally 
at the junction of the limestone beds and slate, although the original form seems to have 
been that of a sulphuret. From these beds the hematitic iron appears to be derived. They 
are always tender and disintegrate rapidly, are magnesian, and frequently contain man¬ 
ganese in addition to the iron. Quartz in fine crystals frequently occurs either in bunches 
or imperfect seams, associated both with albite in twin crystals, and pearl spar. 
RANGE AND EXTENT. 
The Stockbridge limestone, in New-York, Massachusetts and Vermont, trends N. 10° E. 
Commencing at Singsing, it runs a northerly course through Westchester, Dutchess and 
Columbia counties, bordering upon and extending into Connecticut. It passes up the 
valley of the Housatonic, and thence over the dividing ridge into the upper valleys of the 
Hoosic onwards into Vermont, through Shaftsbury, Arlington, and thus on towards Lake 
Memphremagog. I am not, however, well informed as to its entire range north. From 
personal inspection, I found it well developed in Arlington. At Johnson, and farther 
north at Lake Memphremagog, are beds of granular limestone, destitute of graphite, 
which I suppose may be prolongations of the Stockbridge limestone ; still, my examina¬ 
tions have been too hasty and too imperfect among those mountain ranges, to form an 
opinion satisfactory to myself. 
The thickness of the greatest mass of Stockbridge limestone in the Berkshire valleys, is 
about five hundred feet. Of this thick mass, but a very small belt is suitable for marble. 
The absolute white layers are always comparatively thin ; but by sawing the strata through 
the white bands, it is easy to obtain white facings for monuments and other ornamental 
purposes. Where the white masses predominate, silex is a very common element in the 
rock, and therefore it frequently spoils it for the uses to which it might otherwise be 
applied. 
At Williamstown, Massachusetts, the Stockbridge limestone occupies all the base of the 
first high ridge represented on Plate XIII. Thick beds of drift conceal the rock at the first 
terrace above the valley; but above this, the rock appears, and is well exposed up to its 
junction with the slate that crowns all the mountains which appear in this illustration. 
Along the base of this mountain is a fracture whose direction is nearly north and south, 
and the limestone forming the valley was severed from that of the mountain side by an 
uplifting force. 
