272 



UNIVERSITY OF VIRGINIA PUBLICATIONS 



Zircon obtained from sandstone near Ashland, Virginia. 



Accessory heavy minerals in the form of impurities, such as cyanite, 

 garnet, and staurolite, could not be separated from the zircon by the method 

 used, and the results given in the table above are perhaps 2 to 3 per cent 

 too high, though certainly not more. Owing to possible losses through the 

 severe treatment during separation and to the loss of fine zircon in decant- 

 ing, the tests are as likely to show less as more than the quantity present. 

 The results are not, of course, to be regarded as exact, but the method of 

 selecting random specimens from float rock would not warrant more accur- 

 ate determinations. 



It is not thought that the method used, in separating the material intro- 

 duced appreciable errors, as a blank test run on finely pulverized zircon by 

 treating it with a mixture of sulphuric and hydrofluoric acids, showed at 

 the end of three days no trace of zircon in solution. 



The zircon crystals in the material are minute, averaging less than 0.5 

 mm, in diameter. Out of about 96 grams of zircon separated, a small 

 quantity was caught on a sieve of 60 meshes to the linear inch; possibly 

 1 per cent would not pass through a sieve of 80-mesh; nearly 17 per cent' 

 (16.23 grams) passed through an 80-mesh and was caught on a 100-mesh 

 sieve; 77 per cent (74.15 grams) passed through a 100-mesh sieveandwas 

 caught on a 150-mesh sieve; and more than 2 per cent (2.3 grams) passed 

 through a 150-mesh sieve. Most of the accessory minerals (impurities) 

 can be caught on an 80-mesh sieve. 



CHARACTER OF THE SEPARATED ZIRCON CRYSTALS. 



The zircon crj^stals, as separated above, are mostly of short, stout form, 

 though they include a smaller number of elongated forms, possibly one and 

 one-half times as long as thick. In mass they are pinkish or pinkish brow n, 



