Barbour and Fisher — Calcite-Sand Crystal. 451 



Abt. XLTY. — A New Form of Calcite-Sand Crystal; by 

 Erwin H. Barboue and Cassius A. Fisher. 



Until quite recently the knowledge of calcite-sand crystals 

 was confined to a very few occurrences, that of the well-known 

 " Fontainebleaii limestone " being the most important ;'^ here 

 the crystals are rhombohedral in form (— 2E). A few years 

 since sand-calcite crystals of different type from those of 

 Fontainebleau were found on Devil Hill, in the Indian Reser- 

 vation, Washington Co., South Dakota. During the winter 

 the writers have added still another locality, partly in western 

 Nebraska and partly in Wyoming, which yields a third form 



1 2 



Fig. 1. Pen drawing of a scalenoliedron witli rhombohedral terminations 

 illustrating the theoretical form of the sand-lime crystal shown in figure 2. 



Fig. 2. Photographic reproduction of a sand-lime crystal, nearly natural 

 size, the type found at Devil Hill, Indian Reservation, Washington County, 

 South Dakota. 



of sand crystals, namely combinations of acute and obtuse 

 rhombohedrons, constituting a group similar to and quite as 

 interesting as those from Devil Hill, though smaller in size. 



Crystals fromDevil Hill, South Dakota. 



The sand-calcites from Devil Hill, which is the base of the 

 Arikaree sand, vary from single to double, triple, quadruple 

 and multiple crystals, up through clusters and concretions to 

 solid sand-calcite rock, which though solid and compact reveals 

 on fracture, and especially on weathered sections, the indis- 

 tinct hexagonal outlines of its component crystals. 



In point of size they vary from a quarter of an inch (6™°^) to 



*Lassone, Mem. d I'acad. royal, Paris, 1775, p. 65. Haiiy, Traite de 

 Mineralogie, vol. 1, p. 424, 1882. See also Dana, Syst. Min., p. 266. 



