24 NEW YOliK STATE MUSEUM 



ECONOMIC VALUES OF THE LAKE ALBANY DEPOSITS 



Molding sands. Sands of the requisite qualities for use as mold- 

 ing sands appear to be a widely distributed constituent of these lake 

 deposits. They are obtained at present in the localities of the follow- 

 ing shipping stations: near South Schenectady, Carman (on New 

 York Central & Hudson River Railroad, east of Schenectady), Nis- 

 kayuna, Dunsbach Ferry, Elnora, Usher, Round Lake. 



At the South Schenectady locality about 40 acres of 

 farm land have been here worked over and the company 

 holds rights to about an equal additional area. The molding sand 

 occurs in a layer underneath the surface soil at a depth of about one 

 foot. The thickness of the layer is variable, running from a foot 

 or less to three or four feet. In gathering the sand the surface soil 

 is first removed ; the molding sand is then directly loaded into carts 

 and hauled to the car. 



The sand is very fine grained, slightly plastic when wet and of 

 yellowish brown color. A microscopic examination of the sand was 

 made and it was found to correspond closely with the molding sand 

 from Albany county described by Dr G. P. Merrill.^ He states : 

 " the Selkirk molding sand is of a yellow brown color showing under 

 the microscope angular and irregular rounded particles rarely more 

 than .25 mm in diameter, interspersed with finely pulverulent matter 

 which can only be designated as clay. The yellow brown color of the 

 sand is due to the thin film of iron oxid which coats the larger 

 granules. When this film is removed by treatment with dilute hydro- 

 chloric acid, the constituent materials are readily recognized as con- 

 sisting mainly of quartz and feldspar fragments (both orthoclase and 

 plagioclase variety), occasional granules of magnetic iron oxid, and 

 irregularly outlined scales of kaolin together with dustlike material 

 too finely comminuted for accurate determination." 



Theory of the secondary origin of molding sands. In their 

 present occurrence the molding sands do not form a stratum 

 but a surface layer of variable but limited thickness. This 

 layer follows the irregularities of the surface, rising and falling with 

 the surface elevations and depressions. In the Schenectady locality 

 there is a marked unevenness of surface, the difference in elevation of 

 different portions of the area being at least 30 feet. It appears to 

 be a necessary inference from this that surface conditions are a 

 determining cause in the origin of the layer of molding sands. In 



^U. S. Nat. Mus. Report, 1899, p.476, 477. 



