80 NEW YORK STATE MUSEUM 



of the southern belts is probably Precambric, but on the north and 

 east within range of the Taconic disturbance, they may belong to 

 the early Paleozoic. 



Bodies of practically pure serpentine of considerable extent are 

 found on Staten Island and in Westchester county near Rye; they 

 represent intrusions of basic igneous rocks whose minerals, chiefly 

 pyroxene and olivine, have subsequently changed to serpentine. 

 They are not important for quarry purposes, owing to the frequency 

 of fissures and joints and the rather somber color of the exposed 

 parts of the masses. 



The microcrystalline or subcrystalline limestones that are some- 

 times sold as marbles include members of the regularly bedded un- 

 metamorphosed Paleozoic limestones, which locally, show qualities 

 of color and polish that make them desirable for decorative purposes. 

 They range from dense granular varieties to those having a more 

 or less well developed crystalline texture and are often fossiliferous. 

 Inasmuch as they have never been subjected to regional compression 

 or been buried in the earth deep enough to become heated, the crys- 

 talline texture, when present, may be ascribed to the work of ground 

 waters. These circulate through the mass, taking the carbonates 

 of lime and magnesia into solution, and redeposit them in crystalline 

 form. Originally, the limestones were accumulations of lime-secret- 

 ing fossils or granular precipitates, for the most part of marine 

 origin. Some of the localities where these unmetamorphic marbles 

 occur are on the west shore of Lake Champlain, around Plattsburg 

 and Chazy (Chazy limestone), Glens Falls (Trenton limestone) and 

 Becraft mountain and Catskill (Becraft limestone). 



Production. The number of active quarries in the State is small 

 and the annual output falls below that of other quarry materials, 

 with the single exception of granite. There is considerable fluctua- 

 tion, however, in the output, depending chiefly upon the activity in 

 building operations, as the greater part of the product is sold as 

 architectural stone. A single contract for a large structure may 

 make a very apparent difference in the annual total. 



In 1912, there were seven active quarries, with a product valued 

 altogether at $241,847. Nearly one-half of the value, or $114,466, 

 was reported by three quarries in the Gouverneur district. Two 

 quarries in southeastern New York, with one at Plattsburg and 

 one at Glens Falls, contributed the remainder. The figures for the 

 last three years are shown in the accompanying table. 



