THE MINING AND QUARRY INDUSTRY 57 



Long Island and Staten Island, and a few deposits on the north 

 shore of Long Island have been referred to the Tertiary. 



The Quaternary deposits have been formed under various con- 

 ditions, but are more or less directly the result of glacial action at 

 the time when this region was invaded by the continental ice sheet. 

 Some are of morainal character and were laid down under the 

 ice or at the ice front. They consist of stif¥ clay in unstratified 

 masses mixed with boulders, often of large size, that have been 

 ground and polished by erosion. Such deposits have not been 

 utilized to any extent except in one or two localities, owing to their 

 usually limited occurrence and the difficulties involved in their 

 treatment. 



Most of the clay beds that are exploited are of glacial origin, but 

 modified by the sorting action of water. They occur frequently in 

 valley bottoms in basin-shaped areas which are the sites of lakes 

 and ponds formed temporarily by the damming of the natural drain- 

 age by the ice sheet or moraines left on its retreat. The beds range 

 from a few feet up to 50 feet in thickness and rest on glacial drift 

 or bed rock. They are normally of blue color, but the upper por- 

 tion may be weathered to yellow. Beds of sand and gravel are 

 frequently interstratified with them. In the Hudson and Cham- 

 plain valleys which were once occupied by large glacial lakes, clay 

 deposits occur in terraces extending several hundred feet above 

 the present sea level. The clay and accompanying sands were 

 contributed by the streams that flowed into these lakes. 



Long Island. Clay beds outcrop along the north shore and at 

 several points on the main line of the Long Island railroad. The 

 most western occurrence is on Elm point, near Great Neck, where 

 there is a bed of stoneware clay 30 feet thick overlain by gravel 

 and drift. It resembles the Cretaceous clays of New Jersey and 

 probably belongs to this series. Deposits of similar character are 

 found on the east shore of Hempstead harbor, at Glen Cove and 

 vicinity, on Center island in Oyster bay, on Little Neck in North- 

 port bay, and at other localities. The Cretaceous clays are adapted 

 for stoneware and coarser pottery, as well as for brickmaking. 

 Common brick clays extend almost the entire length of the island. 

 They are worked at Garden City, East Williston, Farmingdale, 

 Port Jefferson, Southold and Greenport. 



Staten Island. Important deposits of Cretaceous age are found 

 in the southern part of the island. They are of varied quality, 

 some grades being white and approaching kaolin in composition. 



