$2 Geology, &c. of the Connecticut. 
form are often a foot or more in length, and arranged par- — 
allel to one another; the rock appearing as if bored through 
repeatedly by an augur. The imbedded minerals are cal- 
careous spar, analcime, chlorite,quartz, chalcedony, chaba- 
sie, zeolite, and Professor Silliman has recently discovered 
gypsum™ in a specimen sent him from Dr. Cooley ; a new 
fact we believe in Geology, and one which renders it not 
improbable that this valuable mineral may be found in abun- 
dance along the Connecticut. 
This amygdaloidal greenstone is probably most abundant 
at the lower part of the greenstone ridges ; while the upper 
part is solid and usually columnar. Frequently, however, 
e columns are amygdaloidal to their top, age sometimes, 
as in Deerfield, in passing in the direction of the ridge, you 
will find alternate successions of amygdaloidal and solid 
greenstone columns. On breaking into the interior of the 
former, we often find them a rich reservoir of rare miner- 
als. The cavities are usually small; but sometimes sever- 
al inches in diameter, occupied by quartz and amethystine 
geodes, or chalcedony, or agates, or a peculiar pseudo- 
morphorus quartz to be described when we come to treat 
of particular minerals. The largest and best agates occur 
usually among the greenstone that is not much amygdaloid- 
al, sometimes occupying a cavity, part of which is in one 
column and part in another. They are very frequent, and 
some of those recently discovered by tates in 
Deerfield, are probably the finest yet found in this country, 
A particular account of them will be given in the proper 
place. Prehnite sometimes forms a thin incrustration on 
the columns that are not amygdaloidal; and between the 
joints of those that are so, is sometimes interposed a thin 
coating of various minerals,among which epidote frequently 
predominates, 
Some of the amygdaloid is very vescicular, bearing some 
resemblance to the slag of an iron furnace or la The 
cavities, in certain rare varieties, are various in form; and 
the base is whitish brown, reddish, and even brick red ; 
containing, in the cavities, much prehnite, and this mineral, 
together with calcareous spar, seems, in some instances, to 
be mixed with the greenstone to form the base. An en- 
thusiastic Huttonian would doubtless be gratified to find 
*This gypsum was perfectly fresh—crystalized—white, and retaining its 
water of crystalization.—Editor. 
