244 Notice of a singular Conglomerate, dc. 
Chrysoprase. 
I have lately received from Gen. Field,* of New-Fane, 
Vt., specimens of this mineral found in that town associa- 
ted with serpentine. It closely resembles the chrysoprase 
from Kosemutz, Silesia. a 
Art. VII.—Notice of @ singular conglomerate, and of an 
interesting locality of trap tuff or tufa, in a letter to the 
Sir, . 
I wave had several years in my possession a specimen 
of a very singular conglomerate rock, which | found as a 
rolled mass on the banks of Deerfield river, and of which, 
I have never.met with a description. It may be described, 
as a mica slate, in whichare imbedded numerous rounded peb- 
bles of limpid quartz. ‘These vary in diameter from one 
quarter of an inch, to two inches ; and their colour is light 
gray, or milky, and, In some instances, especially in the 
smaller nodules, they have a strong resemblance to semi- 
opal. They are in general perfectly rounded, may be dis- 
engaged from their bed, and appear precisely like quartz 
pebbles that are found along the banks of rivers. They 
constitute, in general, one half of the rock, and in no in- 
stance, (although I have recently seen numerous specimens, ) 
have I discovered a pebble of any other sort. ‘The base 
of the rock has a schistose structure; but I have not no- 
ticed any thing like planes of stratification. The mica Is 
abundant, age in small plates; and the quartz is gran- 
ular, and may be merely comminuted portions of the im- 
bedded nodules. l : 
It was not merely the peculiar composition of this con- 
glomerate that attracted my attention ; but its locality also. 
Deerfield river, in all its course before it reaches the spot 
where | found this rock, does not pass over, or near, any 
secondary rocks. Its bed is entirely primitive, consisting 
* See Gen. Field’s own notice among the miscellaneous localities —Ep. 
