(172 Report on the Geological Survey of Connecticut. 
and easily separable. Much of it consists almost wholly of feldspar. 
Flags are quarried here of great size and any desirable degree of 
thinness ; and although the transportation by land to market (to 
Norwich) is above fifteen miles, they are yet afforded so low as to 
compete with the Bolton stone.”’ | 
‘‘ Next in importance to the gneiss, the mica-slate of Bolton moun- 
tain deserves to be noticed as a flagging-stone. No material of this 
species has yet been discovered in the United States or elsewhere, 
capable of being compared with this invaluable stone. Slabs five 
feet by eight, and even larger, are furnished by these quarries, whose 
surfaces are as true and smooth, as any granite or sandstone could be 
_rendered by the nicest process of dressing, and yet with a thickness 
not above six or eight inches. The rock derives its color from the 
mica, which is of a silver gray. It is so abundant that its cleavage 
surfaces exhibit no other mineral, and its lustre is no less brilliant 
than that of the Haddam gneiss. ‘The stratification of the rock ts 
extremely uniform and always thin, sometimes apparently consisting 
of upwards of an hundred thicknesses of mica in one inch. The 
layers interposed between the mica in one variety of the rock, consist 
of an aggregate of grains of quartz, feldspar and garnet; but each 
so small as to require a microscope for detection. ‘The use for which 
this stone is especially fitted is for side-walks, market-houses, cellars, 
and foot-paths generally about houses, as well as for water-gutters. 
Its strength is inadequate to the support of carriage-wheels. It 
should, therefore, in the paving of streets, be employed along with 
the Connecticut river gneiss, whose firmness admirably fits it for 
foot-paths across streets and for curb-stones. The quarries extend 
for two miles along the Bolton mountain. The stratum which affords 
the flagging-stone is from fifteen to twenty feet in thickness; and of 
this the upper part, to the depth of six feet is of inferior value, 
affording only asmall proportion of flagging-stone. ‘Above this stra- 
tum is an overlie of nearly forty feet, of dark, gray micaceous lime~ 
stone or calcareous mica-slate. 
‘«¢ The strata dip westerly from 25 to 30°. ‘The thin stratum be-. 
tween the garnetiferous mica-slate and flagging-variety is called the 
diamond-reef by the workmen, on account of the rhomboidal frag- 
ments into which it separates. ‘The labor of quarrying the flagging- 
stone is very considerable. ‘The superincumbent strata require to 
be removed as fast as the workmen advance in the removal of the 
flagging-stone. ‘I'hus, they are obliged to reject more than two- 
