PRIMARY ROCKS. 531 
several of llie small islands of that vicinity. These and the associated hornblende rocks are 
like those on the island of Nevi^-York, and at Hurlgate near Hallet’s cove. 
The gneiss and granitic rocks of the west shore of Westchester county have been described 
while treating of the Metamorphic rocks, as associated with the white limestones. 
4. Mica Slate. 
This rock has a very limited distribution in New-York, Westchester and Putnam counties. 
Where it does occur, it seems to be a rnodificalion of gneiss, the mica becoming predominent, 
while within a short distance the rock resumes its characters of gneiss. No locality was 
observed where there is a prospect of valuable quarries of flagging stone of this kind of rock 
being opened, near water transport. A locality of mica slate, well characterized and fissile, 
may be seen, forming a point in Haverstraw bay, half to one mile northwestwardly from 
Henry I. Cruger’s mansion. This rock assumes the characters of gneiss two or three miles 
north-northeast of the point above referred to, and thence continues its course in the line of 
bearing of the strata. 
5. Augite Rock. 
This rock occurs in a great number of localities in Putnam county, and in a few in West¬ 
chester county. It is sometimes intermixed with felspar, but more commonly it is either by 
itself, or mixed with the various minerals that are usually associated with it. It occurs at 
most of the celebrated mineral localities in the Highlands. It is of all shades pf color, from 
white through grey and green of various shades to black, and from compact through various 
grades of granular to broad foliated masses, in the forms of fassaite, coccolite, common 
augite, sahlite, crystallized augite and diopside. This rock has not been applied to any 
useful purpose. * 
It is believed that this rock might with propriety have been described among the Metamor¬ 
phic rocks. It has rarely been found except in connection with such rocks, and is almost 
constantly associated with scapolite, granular limestone and hornblende. It generally also, 
in Putnam county, has manganesian garnet and plumbago associated. This rock forms 
extensive masses between Anthony’s Nose and Sugarloaf mountains, along the eastern side 
of the Hudson, between the shore and the base of the mountains. 
Between the “ Old silver mine ” and the Hudson about four or five miles south of West- 
Point, it contains large quantities of crystallized, massive and granular manganesian garnet. 
The augite is dark green, and sometimes black, containing plates and hexagonal scales of 
plumbago. This rock scarcely corresponds with augite rock as described in systems of 
geology, as it does not generally contain felspar. Most frequently it is an aggregate of augite 
and scapolite, augite and carbonate of lime, or augite and manganesian garnet, and sometimes 
augite and mica. 
A locality of white or rather grey augite, may be examined on the shore of the Hudson 
about opposite Buttermilk falls, and two miles southeast of West-Point, a little above the 
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