South Dakota 'School of Mines 51 



cut white or colorless quartz crystals, the latter varying from 

 microscopic size to one-half inch or more in length. The finer 

 white crystals much resemble white sugar, hence the name sugar 

 geodes. Selenite, crystalized gypsum, is occasionally present. 

 The origin of the geodes is doubtless closely connected with the 

 origin of the chalcedony veins described elsewhere in this paper. 



DEVIL'S CORKSCREWS. 



Among the interesting materials of the badland fcimations 

 few have given rise to more speculations as to their origin than 

 what are know as the Devil's Corkscrews of the Harrison beds. 

 Devil's Corkscrews, or Daemonelix, as they arc technically 

 called, have been known by the early residents of northwestern 

 Nebraska for many years but it was not until 1891 when Prof. 

 Barbour made a collecting trip to Harrison and the Badlands 

 that these strange objects were brought to the attention of 

 scientific men. What they really represent or how they were 

 formed is still a matter of conjecture. The more typical forms 

 are upright tapering spirals and they twist to the right or to 

 the left indiscriminately. The. spiral sometimes encloses a 

 cylindrical body known as the axis but it is more often without 

 the axis. Sometimes the spiral ends abruptly below but more 

 often there projects from the lower part one or two obliquely 

 ascending bodies placed much as the rhizomes of certain plants. 

 The size of the well developed form varies considerably. The 

 height of the corkscrew portion often exceeds the height of a 

 man while the rhizome portion is ordinarily about the size of 

 one's body. 



They are known to occur especially between the head 

 waters of White and Niobrara rivers chiefly in Sioux County, 

 Nebraska but extend westward as far as Lusk, Wyoming. The 

 vertical range of strata carrying them is approximately 200 feet. 

 Concerning their abundance Prof. Barbour says : "It intrudes 

 itself upon you at every turn. On lands laid bare by erosion 

 the half exposed and weathered tops of countless Daemonelix 

 project. There they stand, bolt upright, till overthrown by the 

 elements. We have picked our way through acres of these 

 fallen spirals. In walls, bluffs, and buttes they are particularly 

 accesible to the collector. 



"It is apparent at a glance that they flourished in numbers 

 of which one can form no conception. Growing closely packed 

 side by side, they are often inextricably entangled and fused 

 together. We have counted as many as twenty or thirty in the 



