same processors find a ready market for exposed aggregate panels. Light-weight aggregates made from 

 shale or clay are used in some types of concrete blocks. 



Potential from marine soiirces.^^ Sand and gravel, though lacking in glamour, nevertheless represent 

 the most widely exploited resource from the surface of the continental shelves (Table 5, Mineral 

 Resources). Although land-based resources are very widespread, many coastal urban areas are 

 experiencing an aggregate shortage due to suburban expansion, the increasingly high cost of real estate, 

 and high transportation costs. This shortage has resulted in a marked rise in price in such urban areas as 

 Los Angeles, New York, and Honolulu. 



Since the demand for sand and gravel is largely centered along the coastlines the potential market for 

 offshore sand and gravel is quite large. Because sea transportation costs are much lower than land 

 transportation costs it will be economically feasible for source areas and markets to be separated by 

 distances much greater than those now feasible for conventional sand and gravel operations. Another 

 advantage is that it is much easier to classify sands and gravels at sea where disposal of water and excess 

 fines can be done with minimum difficulty. 



The continental shelves are primarily depositional areas and large areas are covered by deposits of 

 sand, gravel, and clay. In many areas the sands extend nearly continuously from the beaches to depths of 

 600 feet at the shelf edge, usually a distance of many miles. Much of the sand and gravel on the Atlantic 

 shelf was deposited during Pleistocene time when the sea level stood several hundred feet lower and 

 when melting ice sheets that covered the northern third of the United States were discharging vast 

 quantities of sand and gravel. 



It has been estimated that sand deposits cover about 50,000 square miles of the Atlantic shelf and 

 areas about half as large off the Gulf and Pacific coasts. Some deposits exceed 180 feet in thickness.^" 

 The shelf sands are mostly well sorted, and deposits of various grain sizes can often be found within a 

 100 square mile area. Sand suitable for most requirements can probably be found at one place or 

 another on the continental shelves. The reserves of sand on the shelves are huge and could probably 

 supply demands for many centuries. 



Gravel is not as abundant on the shelf as sand and is commonly covered by sand overburden, but 

 surface gravel layers in some areas are fairly extensive. One widespread gravel layer lies just off New 

 York City and another covers a large part of Georges Bank."* ' Gravel beds 20-40 feet or more thick can 

 also be expected to fill buried river channels that were cut in the shelf during the Pleistocene period of 

 lower sea level. These submerged deposits may contain upwards of 100 milhon tons each but 

 unfortunately the knovm ones are covered by sand 40 to 1 50 feet thick and exploitation may not be 

 feasible unless the sand can also be marketed. 



It appears that an offshore sand and gravel industry, stiU in its infancy, will grow rapidly and develop 

 to substantial size within the next 10 years in some areas. This is based on rising demand; abundance of 

 suitable deposits in shallow water near markets; relative ease with which materials can be recovered, 

 classified, and transported; and possible multiple benefits that might include deepening and widening 

 navigation channels, reducing tidal current speeds, increased mooring areas, and other such factors. 



STAUROLITE"^ 



Staurolite has been separated from placer concentrates in Florida and South Carolina for use as a 

 blending agent in the manufacture of portland cement and as a premium grade product for sand blasting. 

 Any concentrates from placers along the east coast of the United States, including offshore, will 



Summarized largely from Ocean Science and Engineering, Inc. report. 



'**'k. O. Emery, "Geological Methods for Locating Mineral Deposits on the Ocean Floor," in Exploiting the Ocean 

 (Washington, D.C.: Marine Technology Society, 1966). 



'"/Wd; John Schlee, "New Jersey Offshore Gravel Deposit," ftY and gua"^, Vol. 57, No. 6, pp. 80-81, 1964. 



''^W. C. Overstreet, in V. E. McKelvey et al, "Potential Mineral Resources of the United States Outer Continental 

 Shelves," unpublished report of the Geological Survey to the Public Land Law Review Commission, March 1968. 



VII-153 



333-092 0-69— 11 



