June, 1906. New Forms of Concretions — Nichols. 31 



These stalactites are, however, too friable to be preserved. These 

 limonite concretions form by deposition from a sheet of ferriferous 

 water which flows during wet weather along a more permeable layer of 

 dune sand or upon the surface of a comparatively close-packed and 

 impervious stratum. It is evident that this comparatively imper- 

 meable layer is able to form in wet weather some fashion of floor for 

 the stream of iron-bearing waters. This floor is, however, but 

 imperfect and very leaky, so that the limonite stalactites have ample 

 opportunity to form where the water drips through. It is very 

 possible that in the case of these sand-calcite concretions some 

 similar structure of the dunes near Salton has permitted a similar 

 stalactite to form at the base of such concretions as were favorably 

 placed. 



SAND-BARITE CRYSTALS FROM OKLAHOMA 



These specimens (Museum No. G. 1285, Plate XXII) were 

 collected by Prof. Charles N. Gould of the University of Oklahoma 

 and presented by him to this Museum. They are found, according to 

 Prof. Gould, along the outcrop of a belt of red sandstone in Eastern 

 Oklahoma. This belt is about ten miles wide and extends for a 

 distance of fifty or seventy-five miles ' through several counties, 

 particularly Cleveland, Oklahoma and Lincoln counties. Prof. 

 Gould referred to the specimens in conversation as "sand crystals." 

 Dr. Otto Kuntze in a similar way calls them "barite pseudomorphs. " 

 In the catalogue of a Western mineral dealer they are listed as identical 

 with certain " silico-barite concretions" collected in Kansas. An 

 Eastern dealer calls them "gypsum pseudomorphs." It may be 

 inferred from these differing appellations that there is more than a 

 little uncertainty regarding the nature of these objects. 



Twelve specimens which came into the posssesion of the Museum 

 at the close of the St. Louis Exposition vary from 2% to 7 centimeters 

 in diameter and from io>£ to 364 grams in weight. They assume the 

 form of rosettes which are composed of aggregates of tabular crystals 

 resembling lamellar-nodular aggregates of gypsum, barite and other 

 minerals. The faces of the plates are, however, somewhat rounded 

 on the edges as if eroded and hence not sufficiently definite in form to 

 permit of exact measurements or determination. According to 

 Prof. Gould they vary in size from that of a pea to a diameter of five 

 inches. They are found both enclosed in the sandstone and weath- 

 ered out. 



