6 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.60 



Not extracted by a common magnet — Continued. 

 Transparent to translucent — Continued. 

 Color green — Continued. 



Bright green to yellow green and yellow — Continued. 

 Form broken or irregular: 



Luster vitreous; augite, olivine. 

 Luster greasy ; titanite. 

 Color blue of various shades, varying to lavender and gray : 

 Form hexagonal ; corundum. 

 Form bladed ; cyanite. 

 Color gray to brownish gray : 

 Form tetragonal ; zircon. 



Form isometric, rounded; pyrochlore (?), microlite (?). 

 Form broken thin chips, glassy ; obsidian. 

 Color white or colorless (varying to smoky or faintly pink) : 

 Form isometric ; diamond. 



Form hexagonal (prismatic or pyramidal) ; quartz. 

 Form tetragonal, various; zircon. 

 Form monociinic, prismatic ; monazite. 

 Form broken or irregular : 

 Luster vitreous ; quartz. 

 Luster adamantine; zircon. 

 Luster resinous ; monazite. 



The sands studied, about 50 in number, were those preserved in the 

 United States National Museum reference collections. These have 

 been accessioned from various sources, but mainly by transfer from 

 the United States Geological Survey, most of which are those exam- 

 ined by Day in the work cited below. A few are sands received from 

 miners or prospectors for examination and report which have been 

 of sufficient general interest to deserve preservation. The sands 

 in most cases are not accompanied by data as to how they were 

 concentrated or what processes they have been subjected to in the 

 laboratory since they were collected. It seems certain that almost 

 all have been more or less worked over by screening, gravity, and 

 magnetic concentration, and that some are merely fractional portions 

 of the original sand which have been separated by one of the above 

 processes. It is therefore impossible to surmise, in most cases, the 

 quantitative amounts of the several minerals originally present. 

 Thus, it is not known whether the predominance of ilmenite over 

 magnetite, commonly shown in the samples, is actual or due to the 

 magnetite having in large part been extracted by a magnet. Sim- 

 ilarly, some samples show considerable amounts of gold, while others, 

 which from their nature and locality might be expected to be highly 

 auriferous, contain none, the natural inference being that this metal 

 has been removed by amalgamation. 



The localities represented by samples in the collection studied are 

 not as scattered as might be considered desirable, the sands, with a 

 few exceptions, falling into three groups, the first from the bars of 



