482 
GEOLOGY OF THE FIRST DISTRICT. 
3, A slaty variety of a greenish white color, is harder than the preceding, and is fusible upon 
the thin edges by the blowpipe. This last seems to approach jade or saussurite in its cha¬ 
racters, but its peculiarities are probably owing to the admixture of some other minerals, as 
all these varieties seem to pass into each other by almost imperceptible gradation. 
“ Of the magnesian carbonate of lime, several forms occur at the locality in question.* 
There is a thin stratum which is snow-white, very close grained, compact, and has a semi¬ 
opaline appearance. Tt is sometimes described under the name of gurhojite, from its having 
been first found near Gurhof in Austria. According to my analysis, its composition 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 structure, and contain crystals of bronze yellow iron 
pyrites. 
“ 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 picrolile of the more recent 
authors.”* 
2. The bed of limestone northwest of Davenport’s corners, which is on the post road five 
miles northeast from Coldspring, is similar to that at Hustis’s, but not as beautiful, and does 
not exhibit the beautiful minerals of that locality. 
3. This range of limestone crosses the road about one hundred or one hundred and fifty 
yards west of the locality of laumonite and stilbite in Phillipstown, about three hundred yards 
west of Phillips’s mills, and one mile and a quarter east of West-Point. It is white, and 
highly charged with grains of magnetic oxide of iron. Granular hornblende, like coccolite, 
also occurs with the limestone. Hornblendic gneiss and micaceous gneiss, containing pyrites 
and scales of plumbago, also occur associated. 
4. This bed has had excavations made in it, in two or three places between the locality 
above described, and where it reaches the shore of the Hudson about one mile and a quarter 
southwest of Mr. Arden’s; and every place where it was examined, showed imbedded grains 
of magnetic oxide of iron, and in some places, imperfectly characterized brucite and serpen¬ 
tine. 
5. The “ Cotton rock,” as it is called, is at the junction of this bed of limestone with dial- 
* Prof. Beck, Fourth Annual Geological Report of New-York, 1840, p. S6. This locality is the one mentioned in Robinson’s 
Catalogue of Minerals, pp. 145 and 295. It is extremely rich in very beautiful minerals. Phillipstown is a large township, in 
which there are many interesting localities, which I suppose will be mentioned in the Mineralogical Report by Prof. Beck. There 
is probably no individual so well acquainted with them as myself, having for twelve years lived at West-Point, and visited them 
frequently with my mineralogical classes from that institution, and frequently found new ones in our explorations. A list of them 
was furnished to Dr. Horton for Dr. Beck. 
