454: Barbour and Fisher — Calcite Sand Crystal. 



Concretion: silica, 47*94 ; phosphorus, '0 1 ; iron, Fe20g + Al^Og, 

 14-52; lime, CaCOg, 34-24; magnesia, MgCOg, 3*25; undeter- 

 mined, probably manganese, '04. 



Distribution and Geologic Range of Sand- Calcite Crystals. 



The distribution of sand crystals is very wide though they 

 are little known and seldom recognized from the fact that the 

 more obscure forms pass for concretionary sand and receive no 

 attention. They have been personally observed at and around 

 Devil Hill, in the Indian Reservation of South Dakota ; in 

 Sioux County. Nebraska; in the E'orth Platte region in 

 Nebraska, at Goshen Hole, Bates Hole, and intermediate points 

 in Wyoming. 



The larger crystals present no such disparity between the 

 component sand and gravel grains and the crystal itself as do 

 the lesser ones, hence their forms are defined and perfectly 

 apparent. Such forms are restricted and very local in area. 

 Those at Devil Hill occur in enormous quantities along about 

 100 yards of exposure. The total extent of the bed, which is 

 but a mere remnant of the original, is scarcely one acre. 

 Those from the region of the North Platte river, at or near 

 the Nebraska line, seem to be even more local, and are very 

 scattered in number. The same seems to hold true of those in 

 the Goshen Hole country, which may be classed with the North 

 Platte region, both producing the same crystalline forms shown 

 in figure 4, though differing in horizon. There are but the 

 three above named localities known in this country which pro- 

 duce these crystals. In France, at Fontainebleau, the crystals 

 are similar in physical properties to those from the Great 

 Plains though differing crystallographically, inasmuch as they 

 are simple unmodified rhombohedrons. 



In vertical range these forms occur in greatest numbers in 

 the Arikaree, though found as low as the Chadron sands at the 

 base of the Oligocene. In the basal sands of the Laramie of 

 Wyoming occur numerous examples of the obscure or concre- 

 tionary type. 



Locality of sand-calcites. 



^. f Devil Hill, S. D. 



IVliocene , gj^^^ ^^ Nebraska 



Tertiary (Arikaree) ^ ^^ ^^ Wyoming 



Bates Hole, Wyoming 

 Oligocene c 



(Chadron sand) ] Mitchell region, Nebr. 



i South of Buffalo, Wyoming 

 Cretaceous Laramie } Obscure crystals or concre- 



( tionary sand 



University of Nebraska, Lincoln, Nebr. 



