168 



E. H. BARBOUR — SAND CRYSTALS 



Cross, of York, who had received them, without data, from Doane col- 

 lege, Crete, Nebraska. Drawings were made of the groups, and the matter 

 was presented the same year to the Nebraska Academy of Science. 

 Although diligent inquiry was made, nothing could be learned of their 

 locality until the Reverend J. M. Bates, of Long Pine, informed the writer 

 of the exact spot, which was visited as promptly as possible. The place 

 was studied, a large amount of representative material collected, and 

 photographs secured. 



The mode of occurrence of these cr3^stals seems most unusual and re- 

 markable. In a bed of sand scarcely 3 feet thick, and so soft as to re- 

 semble the sand of the seashore, occur these crystals in numbers which 

 can best be figured in tons. We dug them out with our bare hands. 

 They were mostly single crystals, with numerous doublets, tri})lets, quad- 

 ruplets, and multiplets. In other words, every form from solitary crys- 

 tals to crowded bunches and perfect radiating concretions was obtained. 





Fi(;l'kk 2.— Sand Rock (it D< vil Hill, Soidli Dakota. 



It is made up of mind crystals, as is revealed by certain hexagonal reflections and Ity an irregular 

 prismatic structure developed on weathering. 



It was a matter of especial interest in the field to note that at the 

 bottom of the layer the bulk of these sand-lime crystals are solitary ; one 

 foot higher there is an evident doubling of the crystals, until within 

 another foot the}^ are in loosely crowded clusters ; a little higher in closely 

 crowded continuous clusters, })ried out in blocks with difficulty ; still 

 higher they occur in closely crowded concretions in contact with one 

 another, making nearly solid rock. A little higher this mineralizing 

 process culminates in pipes, compound pipes, and solid rock composed 

 wholl}^ of crystals, but so solidified that their identity is lost, and is de- 

 tected only by a certain reflection of light, which differentiates the other- 

 wise invisible crystal units b}^ showing glistening hexagonal sections. 

 There could not have been a more gradual and beautiful transition, and 

 all confined to a bed 6 or 8 feet in thickness. This is shown juctorially, 

 though inadequately, in plates 13 and 14. Plate 14, figure 2, shows a 



