SAXD AND GRAVEL. 



241 



The following physical tests made by Ries on the samples of sand from 

 Virginia further serve to show their general character: 



Locality 



Eedford yellow sand collected at pit 

 in Manchester 



Coarse sand, Haibaugh pit, Richmond 



Nsed molding sand, Redford pit, Rich- 

 mond 



Sand from near Petersburg 



Blandf ord pit, Petersburg 



Armstrong pit, Petersburg 



Sand from near Standard Brick Com- 

 pany, south of Suffolk 



Griffitji's pit, Fredericksburg 



Curlis pit, southeast of Lanexa 



One mile south of Layton 



20 



1.51 



42.48 



5.34 

 0.73 

 3.03 

 0.09 



0.12 

 0.19 



6.68 



40 



1.26 

 12.90 



14.73 

 2.34 

 1.41 

 0.41 



0.29 



0.19 



0.01 



28.13 



60 



1.27 



6.16 



10.41 

 8.76 

 0.97 

 2.21 



13.00 

 0.39 

 0.08 



51.66 



80 



0.56 

 0.85 



1.28 

 2.21 

 0.40 

 2.67 



6.56 

 0.19 

 0.07 

 3.18 



100 



6.27 

 1.70 



14.61 

 12.25 



2.61 

 17.37 



38.02 

 0.98 

 1.11 

 3.75 



lOOX 



71.69 



8.58 



59 37 

 14.79 

 48 . 32 

 53.20 



35.18 



81.92 



86.77 

 2.63 



Clay 



16.52 

 26.44 



3.52 

 30.54 



41.87 

 19.02 



6.03 

 15.97 

 19.57 



2.16 



Along the tide-water streams on the sandy beaches may be seen thin 

 layers of heavy black sands, composed largely, if not entirely, of grains of 

 magnetite. These beaches are sometimes covered to a depth of several inches 

 with almost pure sands of this character, although usually the fine sandy 

 beaches contain layers of black sands interbedded with fine yellow sands. 

 In some places along the lower Rappahannock River it would be impossible 

 to obtain sands of this character in considerable quantities. It is doubtful 

 whether the sands will ever prove valuable as an iron ore but it is possible 

 that other minerals of greater value may be. present with the magnetite. 

 Investigations recently carried on by the United States Geological Survey 

 on the black sands of the Pacific Coast have revealed the presence of mag- 

 netite, ilmenite, chromite, zircon, and monazite, all of which have a com- 

 mercial value in the arts. In some places such sands contain gold and 

 platinum. Although the black m.agnetite sands of Virginia are probably of 

 little value in comparison with the much more abundant deposits on the 

 Pacific slope, it is desirable that their composition be determined. 



Gravel. — The Lafayette, Sunderland, Wicomico, and Talbot formations 

 furnish the principal gravel deposits of the Coastal Plain, although the 

 Patuxent and Patapsco formations also contain locally considerable beds of 

 gravel. The last two formations have a very limited outcrop in Virginia so 

 that their economic importance as a source of gravel is not great. The 

 other four formations, however, contain an abundance of gravel suitable for 

 road-making, and their Avide distribution renders them of particular value 

 throughout the greater portion of the region. One or another of these 

 formations is present almost everywhere in the Coastal Plain except on the 

 steeper slopes, and even in such places the talus consists largely of Pleisto- 



16 



