334 Prof. Beck on Igneous Action, as exhibited in New York. 
well defined. They usually have a saggy aspect, their angles 
being obliterated, and their surfaces covered with a kind of glaze; 
while not unfrequently groups of crystals have coalesced into one 
mass or united together like the glass beads found among the 
ruins of the great fire in the city of New York, (1835.) ‘These 
remarks will apply also to some of the other minerals anaes 
with the scapolite, but the change is rarely so marked. 
Facts similar to the above have been observed in Orange Coun- 
ty, where the white limestone is frequently in beds in granite and 
gneiss. In the vicinity of Edenville the apatite found in this 
rock, often has the bent form and glazed appearance so charac- 
teristic of this mineral in St. Lawrence County; and at Amity the 
so called idocrase, has sometimes two or three perfect faces, while 
other parts of the crystal look as if they had been softened by 
heat, and in this softened state had accommodated themselves to 
the little cavities and fissures of the limestone. 
_ It may here be remarked, that I have not hitherto observed any 
appearances like those above described in the dolomitic limestones 
of the southern part of New York. It is true the pseudomorphic 
forms of hornblende and pyroxene which I noticed in a for- 
mer paper are very abundant; and these it will be observed, I 
have proposed to refer to an agency similar to that which seems 
to have produced the peculiarities exhibited in the minerals of the 
white limestones. It should be borne in mind, however, that for 
some reason or other, there is a greater poverty of minerals in the 
dolomites than in the latter rocks. In the former, the different 
varieties of hornblende and pyroxene are almost the only species, 
if we except those found in a few metallic veins, some scales of 
mica, and thin layers of jasper or hornstone. On the other hand, 
the white limestones abound in spinelle, chondrodite, crystallized 
mica, feldspar, tourmaline, apatite, scapolite, sphene, graphite, 
hornblende, pyroxene, and several others which it is not neces 
sary to enumerate. 
I proceed now to notice some peculiarities of the minerals found 
in gneiss and mica slate. The occurrence of crystallized garnets: 
in these rocks has been adverted to by Mr. J. Phillips, as an evi- 
dence that the whole mass has been subjected to a pervading 
high temperature. “The occurrence of garnets,” he adds, “10 
mica schist and gneiss is entirely unconnected with any local 
effect of heat, derived from particular masses of granite, green- 
