JUNE, 1906. New Forms oF CONCRETIONS—NICHOLS. ne 
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 10% 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. 
