ON OOLITES AND SPHERULITES: 
WALTER H. BUCHER 
University of Cincinnati 
COLLOID-CHEMICAL INTERPRETATION OF ORIGIN OF OOLITES 
Schade’s work.—The most important contribution toward a 
satisfactory interpretation of the origin of odlites and related 
structures was made by a member of the medical faculty of the 
University of Kiel, H. Schade, in 1909 and 1010, in his papers on 
the origin of urinary calculi and on the formation of concrements.? 
In these he demonstrated experimentally that concretionary bodies 
form when a substance passes from the state of an emulsion colloid 
(or “‘emulsoid’”’) to that of a solid, and that if the change leads to 
the crystalline state the resulting structure is radial if the substance 
is pure; if, however, other substances, colloid or crystalloid, are 
precipitated along with it a concentric structure is developed. 
Corresponding with this law, natural holesterin gallstones, when 
80 to go per cent pure, show a radial crystalline structure, while 
gallstones containing 25 per cent or less holesterin exhibit perfect 
concentric lamination. 
Observations on iron chloride.—A substance which lends itself well 
to a demonstration of the process involved, because it requires no 
special preparation, is the commercial hydrated iron chloride. A 
t A rock is called ‘‘odlitic,” or an ‘‘odlite,”’ if it contains or consists of small grains 
or units of dominantly concentric structure. A rock is called ‘“‘spherulitic” (but not a 
spherulite) if it contains or consists of small grains or units of dominantly radial 
crystalline structure. An individual grain of a spherulitic rock is called a “‘spheru- 
lite.’ For an individual grain of an odlite the term “‘ovulite” might be used, which 
appears to be preferable to Kalkowsky’s ‘“‘odid” not only for symmetry’s sake. In 
this paper the term ‘‘spherite”’ will be used for all grains of the same origin irrespective 
of their structure. 
2 Heinrich Schade, ‘‘Zur Entstehung der Harnsteine und dhnlicher konzentrisch 
geschichteter Steine organischen und anorganischen Ursprungs,” Zeztschr. fiir Chemie 
und Industrie der Kolloide, IV (1909), 175-80; ‘‘Ueber Konkrementbildungen beim 
Vorgang der tropfigen Entmischung von Emulsionskolloiden,” Kolloidchemische 
Bethefte, I (1910), 375-90. 
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