280 DKSCRIPTIVE 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 with 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 white. 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 eiflo- 

 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 Sciaicet of Pliikdelpkia, III. 129. 



