40 
[Assembly 
The magnesia contained in either of these minerals would furnish, by 
combination with sulphuric acid, upwards of two hundred parts of sul- 
phate of magnesia or epsom salts, in the form in which it is ordinarily 
sold in the shops. Moreover, the sulphate of magnesia, thus obtained, 
may be decomposed by carbonate of soda or potash and produce carbo- 
nate of magnesia, which, as well as the sulphate, is used for medicinal 
purposes.* By this operation, when serpentine is employed, a large 
quantity of Venetian red is also procured, as that mineral contains a 
considerable proportion of oxide of iron. This manufacture is now car- 
ried on near Baltimore, in Maryland, and there seems to be no reason 
why it may not be profitably pursued in the vicinity of New- York. 
63. Serpentine, similar in every respect to that found on Staten-Is- 
land and at Hoboken, in New- Jersey, occurs in considerable abundance 
in the counties of New-York, Westchester, Putnam, Rockland and 
Orange; and extensive deposits of the same mineral are also found in 
the county of St. Lawrence. 
The beautiful green colour of serpentine, and the fine polish which it 
takes when pure, give it great value as an ornamental marble. When 
mixed with granular limestone it forms the celebrated verd antique. Un- 
fortunately in almost all the localities in the southern part of the State, 
at least so far as they have been explored, the serpentine, although in 
great abundance, is so mixed with carbonate of magnesia, asbestus and 
other magnesian minerals, as to render it unfit to be worked as a mar- 
ble. Thus a block obtained from a quarry in the county of Westches- 
ter, concerning which high expectations had been raised, was found to 
have an unequal degree of hardness in its different parts, and to be fill- 
ed with seams and nodules of other magnesian minerals w^hich could not 
be polished, or were too friable to sustain the rough usage which is re- 
quired for the dressing of marble. 
Prof. Emmons informs us that there are several localities in St. Law- 
rence county in which the soundness of the serpentine rock is remarka- 
ble; and the only impediment^to the introduction of this article for orna- 
mental and useful purposes, he thinks, is the expense of transportation. 
At Pitcairn is a fine locality of verd antique. The colours are green and 
white, arranged in the usual forms of clouded marble. The serpentine 
has a bright green colour, and belongs to the variety usually called pre- 
* Should the preparation of these salts of magnesia become important, the dolomites or dou- 
ble carbonates of lime and magnesia which occur at Sing-Sing and elsewhere, may be also ad- 
vantageously employed for that purpose. The double carbonate is first to be calcined and then 
treated by sulphuric acid, or sulphate of iron. There is thus formed an insoluable sulphate of 
lime and a soluble sulphate of magnesia, which can be easily separated. 
