280 
DESCRIPTIVE MINERALOGY. 
Richmond County. This mineral occurs in thin strata in the serpentine and magnesian 
marble near the Quarantine. It has a white streak and powder. Sectile. It adheres to the 
tongue. A specimen, according to my analysis, was found to contain 
Silica,_..... 41.00 
Magnesia,_..... 41.26 
Water,... 13.50 
Lime,. . 2.39 
Peroxide of iron, with a little alumina, ...... . 1.85 
This is nearly identical in composition with the marmolite of Nuttall, found at Hoboken, 
N. J., and with the magnesite from the Bare hills near Baltimore. Both of these, indeed, 
according to Mr. Vanuxem, agree with precious serpentine from Newburyport, Mass.* There 
is, however, some difference between these minerals in regard to their structure. 
Rockland County. Magnesite, or kerolite, of various shades of colour, as dull white, 
greenish and greyish white, and dark green, is found in narrow veins, seldom above an inch 
in width, in the trap dykes which pass up the northwestern face of Stony point. It is asso¬ 
ciated witli other magnesian minerals, and is often traversed by thin veins of a beautiful 
silky amianthus. Some of the specimens can scarcely be distinguished from those of 
deweylite, in colour and other characters. Its hardness is from 2.0 to 2.5. It yields readily 
to the knife. Powder rvhite. Infusible by the blowpipe, except in very thin fragments, and 
then the edges are slightly rounded, and the mass becomes of a lighter colour. 
The following is the composition of the Stony point mineral, viz : 
Silica,. 37.40 
Magnesia,.... 32.56 
Oxide of iron,..... 10.05 
Water,..... 14.60 
Alumina,... 5.35 
Oxide of manganese, .......... trace. 
It differs from serpentine, and indeed from most of the varieties of magnesite, in the larger 
proportion of oxide of iron. In this respect, it is more nearly allied to picrolite than to any 
other mineral (see Serpentine, page 274). 
Westchester County. This mineral is found in thin veins and in nodules in serpentine, 
in several parts of this county. At New-Rochelle, it is often white, and has an earthy efflo¬ 
rescent appearance exactly resembling some of the specimens found on Staten island. It is 
sometimes stained apparently by chrome iron ore. Occasionally the plates are highly polished 
on one or both sides, as if they had been subjected to the pressure of a very smooth surface 
while in a dissolved state. 
Journal of the Academy of Natural Sciences of Philadelphia. III. 129. 
