SERPENTINE. 
87 
New York and the British provinces, clouding, as it were, the 
mass, while in the latter places it is in distinct grains and masses, 
which are perfectly circumscribed, and may be detached by a 
blow, when aided by previous decomposition. 
The serpentines of St. Lawrence county, and which are often 
associated with the earthy oxides of iron, contain angular 
pieces of quartz, from a tenth to half an inch in diameter; the 
quartz is not incorporated with the rock, yet it is closely in¬ 
vested with serpentine, and is perfectly separated from it by 
disintegration. 
The serpentine of Cornwall, Eng., is associated with dial¬ 
lage rock, and is traversed by veins of this substance, as well 
as by granite. Our serpentines very rarely contain diallage. 
The dark green serpentine of Westfield, Mass., contains schiller 
spar. It appears then that it is traversed by other rocks, but 
I have not seen that the different geological writers have ob¬ 
served serpentine traversing in this mode, other rocks, except 
in Tuscany. Yet it may have been observed, at many other 
places, but regarded as not worthy of attention. 
In the serpentine belt of Port Henry, the mixtures of serpen¬ 
tine and other minerals decompose and leave a scoriaceous mass, 
like calcareous tufa, as if there was first a deposit or formation 
of a very porous mass, which was afterwards filled by infiltra¬ 
tion with carbonate of lime. I know of no true serpentine so 
connected with sedimentary rocks as to give a clue to its age, 
excepting that associated with the waterlime near Syracuse. 
In St. Lawrence county, iron ore and serpentine are somewhat 
blended with the Potsdam sandstone. As it occurs in this 
country, it must be regarded as one of the most ancient of our 
rocks. The specific gravity of this mineral is 2' 55. 
Serpentine is a hydrous bisilicate of magnesia. It is com¬ 
posed of 
Silica, 
41-89 
Magnesia, 
40-24 
Oxide of iron, 
3-38 
Water, 
15-20 
