THE CRYSTALLOGRAPHY AND CHEMICAL COMPOSITION 



OF CREEDITE. 



By William F. Foshag, 



Assistant Curator, Division of Mineralogy, United States National Museum. 



INTRODUCTION. 



The mineral creedite was found by Dr. E. S. Larsen, of the United 

 States Geological Survey, in the fluorite deposits of Wagon Wheel 

 Gap, Creede Quadrangle, Colorado, and was described by Larsen 

 and Wells. 1 Since their description Doctor Larsen has collected 

 a large suite of specimens which has now been deposited in the 

 United States National Museum (Cat. No. 93117, U.S.N.M.). This 

 material is better suited for study than the original and contains 

 a number of specimens showing well-developed and measurable 

 crystals. At Doctor Larsen's suggestion this mineral was further 

 studied and the writer wishes to express his appreciation for the 

 interest taken by that gentleman in this investigation. 



OCCURRENCE. 



The creedite was found in two modes of association. One type 

 of occurrence is with fluorite, either as crystals in cavities or as 

 embedded radiated masses of crystals in the white, sacharroidal spar. 

 The fluorite itself is banded and shows a weak radiated structure. 

 Very minute crystals of hematite are sometimes found in the cavities 

 in the fluorite masses. 



The second type shows loose, doubly terminated crystals embedded 

 in a white, evenly textured clay described by Larsen and Wherry 2 

 as halloysite. These crystals range up to 1 centimeter in size. Their 

 distribution in the halloysite is very uneven, ranging from a few 

 scattered crystals to masses of almost pure creedite. Rarely small 

 groups of divergent crystals are met with in this clay. 



i Proceedings of the National Academy of Science, vol. 2, p. 360, 1916. 

 ' Journal of the Washington Academy of Sciences, vol. 7, p. 178, 1917. 



Proceedings U. S. National Museum, Vol. 59-No. 2376. 



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