34 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



road running west from Chester station. This company has ah-eady put 

 upon the market a hirge quantity of stone of the first quaUty. The rock is, 

 when poHshed, a clear, dark gray — too dark for many purposes — and when 

 left with a rough surface is almost white, producing a marked contrast 

 where the two kinds of sui-fixce are juxtaposed. The "sap" of the stone in 

 the quarry is thin and white, showing it to be very durable, and the pyrite, 

 which exists in small grains, seems not to be subject to oxidation, unlike 

 that in the thin-bedded portions of the same rock. If it shall prove equally 

 changeless in the worked surfaces after long exposure, the deposit is of great 

 importance, as flawless blocks of the largest dimensions can be obtained, 

 and the extent of the quarry rock is very great. 



The gneiss enters the area of the map again at the northwest corner of 

 Blandford and extends, with similar characteristics, down the western side 

 of the town, widening to the east so as to occupy the whole width of Tolland 

 and half that of Granville. 



Following the band across Blandford, one finds it supper portion, nearest 

 the mica-schist, to be everywhere thin-fissile, nisty, contorted, and more or 

 less shot through by granitic veins; and where it widens out to the south 

 the increased area seems to be occupied by these upper thin-fissile biotite- 

 gneisses and worthless rocks, and west of Tolland the granitoid gneiss 

 either passes down or has run out entirely. 



In some places in Tolland the rock a^^proaches so closely the most 

 feldspathic variety of the next series — at the blacksmith shop in fjie village 

 even containing large garnets — that I have questioned whether one or more 

 folds of this series are not included in the older gneisses. 



It extends south into Connecticiat as the western paii; of Percival's K 2,' 

 from which, on the east, the mica-schist is not separated. Far to the east 

 the same gneiss rises again from beneath the hydromica-schists east of 

 South Mountain, in the southern portion of Granville. It is here a gran- 

 itoid gneiss of the common type, which extends southward into Connecticut, 

 and is marked I 2 upon Percival's map. 



PETROGRAPHICAL DESCRIPTION. 



1. GranUokl gneiss from Clark Hill quarries, Middlefield. "Finest 

 quarry stone." 



■J. G. Percival, Reiit. Geol. Coiin., 1842, p. 113. 



