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chiefly on account of the interesting localities which occur at Cold 
Spring and in Philipstown. The latter, on the farm of Mr. Hustis 
about five miles south of the village of Fishkill, is particularly vi^orthy 
of attention, not only for the number of interesting minerals which it 
affords, but as showing the manner in which allied species run into 
each other. The facts here presented prove how important it is in many 
cases carefully to examine the localities of minerals before we decide 
with certainty upon their specific characters. 
In a bed of white limestone running parallel with the granite and 
which is of small width and is situated about a quarter of a mile from 
the New-York road, we have the following minerals, viz : Precious 
serpentine, of which there are several varieties. The first, has a con- 
choidal fracture and presents various shades of green and yellow and 
is variously disseminated through the limestone and other minerals. 
2. A slaty variety, having a dark green colour. It sometimes breaks 
into rhomboidal prisms and is very hard and compact. 3. A slaty va- 
riety of a greenish white colour, is harder than the, preceding, and is 
fusible upon the thin edges by the blow-pipe. This last seems to ap- 
proach jade or saussurite in its characters, but its peculiarities are pro- 
bably owing to the admixture of some other minerals, as all these va- 
rieties seem to pass into each other by almost imperceptible gradation. 
Of the magnesian carbonate of lime several forms occur at the lo- 
cality in question. There is a thin stratum which is snow-white, very 
close grained, compact and has a semiopaline appearance. It is some- 
times described under the name of Gurhofite, from its having been first 
found near Gurhof, in Austria. According to my analysis its compo- 
sition is as follows, viz : 
Silica, 6.50 
Carbonate of lime, 66.75 
Carbonate of magnesia, 26 . 50 
Other specimens of this mineral have fibres of asbestus running 
through them and they sometimes have a bluish tint, a slaty struc- 
ture, and contain crystals of bronze yellow iron p3rrites. 
Asbestus, especially in the amianthoid form, is indeed largely mixed 
with the minerals already noticed. The beautiful silky fibres which 
run through the serpentine and magnesian limestone in various parts of 
this ridge may belong to the picrolite of the more recent authors. But 
