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NEW YORK STATE MUSEUM 



apparent change. Exposure to a temperature of 1200 to 

 1400 degrees F. caused vitrifaction, destruction of color 

 and impaired the strength so that the specimen crumbled 

 with a blow. The greater part of the product of these quarries 

 is in the form of paving blocks and is shipped to western cities, 

 principally Cincinnati and Chicago. The International Granite 

 Company of Montreal uses a large amount for monumental work 

 and building. Examples of this granite can be seen in the large 

 columns of the Senate Chamber of the New Capitol, Albany, and 

 in the Nordheimer building in Montreal. 



Trap-Rocks. 



Trap-rock or trap is the common name given to a class of 

 eruptive rocks because of a structural peculiarity, and has no 

 distinctive significance in mineralogical composition. The rocks 

 of the Palisade mountain range and of the Torn mountain, which 

 extends from the New Jersey line, on the west shore of the 

 Hudson river to Haverstraw, are known as trap-rocks. There is 

 an outcrop on Staten Island, near the north shore, where a large 

 amount of stone has been quarried at the so-called "granite 

 quarries." 



The trap-rock of the Palisades range is a crystalline, granular 

 mass of a plagioclase feldspar (labradorite usually) augite and 

 magnetite. It is generally finer- crystalline than the granite. 

 The colors vary from dark gray through dark green to almost 

 black. 



This trap-rock is hard and tough, but some of it is split readily 

 into blocks for paving. It has been used extensively in New 

 York and adjacent cities for street paving, but since the intro- 

 duction of granite blocks this use has nearly ceased. On account 

 of its toughness it makes an admirable material for macadamizing 

 roadways. It is so hard that only rock-face blocks are used in 

 constructive work. Several prominent buildings in Jersey City 

 and Hoboken are built of it. There is a large quarry on the 

 river at Rockland lake, the output of which is for street work 

 and road material almost exclusively. There are also quarries 

 at Piermont and at Graniteville, Staten Island. 



