THE MINING AND QUARRY INDUSTRY I9O9 87 



erly speaking trap is a fine grained, dark colored igneous rock 

 resulting from the cooling of a mass of molten material intruded 

 into other rocks. It usually follows a vertical fissure and is 

 known as a dike, or spreads horizontally between beds of strati- 

 fied rock and is known as a sill or sheet. In appearance it is 

 black or greenish black in color, fine grained audi shows a crystalline 

 structure. Under the microscope, in thin section, it is seen to be 

 composed of lath-shaped feldspar crystals, co^ntaining dark collored 

 pyroxene, olivene etc., in the interstices, the whole interlocked in 

 such a manner as to give the rock its well known toughness. 

 This toughness, as well as its cementing or bonding power, 

 has given it a preeminent place as a road material for macadam 

 roads. Whatever the lower courses may be, trap rock top dress- 

 ing is usually specified. 



Aside from its use as crushed stone, it has little demand. 

 Although dressed and polished blocks present a handsome ap- 

 pearance, the cost of dressing and lack of demand have pro- 

 hibited its use for such purposes in this State. In the New 

 England States, related rocks are cut and polished as " black 

 granite." 



The main supply of trap in the State, comes from the Pal- 

 isades on the lower Hudson river in Rockland county. This 

 sheet of diabase is from 300 to 800 feet in thickness and has an 

 outcrop of 70 miles, extending into New Jersey. It presents a 

 practically unlimited supply of trap and large plants are in 

 operation in both New York and New Jersey. The only other 

 active locality in the State is near Greenfield, Saratoga co., 

 where a trap dike is being quarried and crushed. Other locali- 

 ties, formerly active but now idle, are Port Richmond, Rich- 

 mond CO., Northumberland, Saratoga co., and Fort Ann, Wash- 

 ington CO. 



The production for the year 1909 amounted to 1,095,331 cubic 

 yards valued at $1,061,428, as against a value of $723,773 in 

 1908 and $941,627 in 1907. About 80 per cent of the total was 

 used as road metal, the remainder for concrete work and bal- 

 last. Six firms were in operation in, Rockland county, the quar- 

 ries situated at Haverstraw, Rockland Lake,. Mt Ivy and West 

 Nyack. One firm was in operation in the town of Greenfield, 

 Saratoga co. 



Among the changes in the industry were the formation of 

 the Haverstraw Crushed Stone Co., taking over the Long Clove 



