QUARRV MATERIALS OF NEW YORK 1 85 



gneissoid appearance, but lack the schistosity of the Grenville 

 gneisses, are prevaihng reddish or gray in color and belong mostly 

 to the biotite and hornblende varieties of granite. They form 

 bosses of some size and also sills and dikes, while small offshoots 

 cut through the sedimentary gneisses in a network of interlacing 

 veins. They exert noticeable contact effects upon the limestones 

 which in their vicinity may contain such minerals as tourmaline, 

 vesuvianite oyroxene, tremolite, fluorite etc., often well crystallized. 



THE GOUVERNEUR MARBLE 



The crystalline limestone in the area about Gouverneur has 

 furnished most of the marble that has been quarried in the Adiron- 

 dack region. The area is a part of the belt which extends from 

 the town of Canton, St Lawrence county, to near Antwerp, in 

 Jefferson county, and which is traversed for much of the distance 

 by the R. W. & O. branch of the New York Central Railroad. 



The limestone in general is medium to coarse crystalline and white 

 or light gray in color, but sometimes a dark blue as in one or two 

 of the quarries. It is a calcite limestone, with a varying but gener- 

 ally small percentage of magnesia. The carbonates amount to about 

 95 per cent of the whole mass, of which nearly 90 per cent is 

 calcium carbonate. Rarely the magnesia assumes sufficient import- 

 ance to characterize the rock as a dolomite. The change from a 

 calcite-limestone to dolomite takes place abruptly, but whether it 

 reflects an original variation in the conditions of deposition or is 

 due to secondary processes after the strata were laid down, is 

 not clear. In the former case it would be expected to find the 

 variation related to the bedded structure, but such relation can not 

 be established. The occurrence of dolomite is quite local and un- 

 important as compared to the great body of limestone. On the other 

 hand, the limestone shows well-marked zones or bands parallel to 

 the bedding in which quartz is abundant and which seems to be 

 the result of impurities included when the rock was being deposited. 



The following analyses illustrate the chemical composition of the 

 Gouverneur marbles. No. i is based on a sample from the Extra 

 Dark quarry of the St Lawrence Marble Quarries ; no. 2. quarry of 

 the Gouverneur Marble Co ; no. 3, Rylestone quarry ; and no. 4, 

 Northern New York quarry. No. 5 represents the dolomitic marble, 

 formerly worked by the White Crystal Marble Co. Nos. i, 2 and 3 

 are by R. \\'. Jones of the State Museum. 



