Geology of Massachusetts. 23 
hearths and walls of furnaces. Prof. Dewey says that he has ‘seen 
this stone after it has sustained the highest heat of the furnace for 
months, and found its surface merely glazed by the high tempera- 
ture.” It was transported to the iron works in: Bennington, Vt. until 
a similar rock was discovered in that town. It occurs also in Wil- 
liamstown. What peculiarity this rock possesses, that renders it able 
to resist a high temperature, I do not know. 
Another valuable variety of quartz rock is found near the quarry 
above mentioned. But its use, as well as that of another variety in 
Cheshire, will be noticed subsequently. 
Mica Slate. 
This rock is generally more uneven or tortuous in the structure of its 
layers, than any rock in the State. But, like gneiss, its layers are 
sometimes remarkable for their regularity. It then forms an admi- 
rable stone for flagging, for hearths, and for situations where there is 
an exposure to a moderate degree of heat. ‘The variety that occurs 
in Goshen and Chesterfield, Hampshire county, is perhaps the best 
in the State for these purposes; and in these places, particularly in 
Goshen, it is quarried to a considerable extent. In some cases this 
rock approaches so near to argillaceous, or roofslate, that it is employ- 
ed for common gravestones. In Halifax, Vt., there is a quarry of this 
character; and, I believe, also in Chesterfield, Mass. Sometimes it 
forms excellent whetstones; and from the quarries in Enfield and 
Norwich, large quantities are obtained and extensively used. 
Talcose Slate. 
The principle value of this rock, in an economical point of view, 
is derived from its power of resisting high degrees of heat. ‘The 
greater the proportion of talc in its composition, the more valuable is 
it in this respect. A very fine stone of this description, for the lining 
of furnaces, is quarried in Stafford, Ct., and it is employed to some 
extent in the furnaces in Massachusetts. I do not know of any quar- 
ry of this kind in our own state; but undoubtedly such might be 
opened ; since almost every variety of talcose slate exists here. In- 
deed, I am informed by the Rev. Mr. Colton, of Amherst Acad- 
emy, that talcose slate, equal to that in Stafford, may be dug in 
Monson. 
In Plainfield and Hawley a variety of talcose slate occurs, in which 
are disseminated numerous crystals of black hornblende. The tale 
