368 WHERRY AND LARSEN : RHODOCHROSITE AND SIDERITE 



The compositions and indices of refraction of four siderites 

 are given in Table 2 for comparison. The data for the siderite 

 associated with the cryolite from Ivigtut, Greenland, and those 

 of the mineral from the Spokane locality are new. The latter 



TABLE 2 

 Indices of Refraction of Analyzed Specimens of Siderite 



"Analysis and sp. gr. by E. T. W., optical data by E. S. L. U. S. Nat. Mus. 

 Cat. No. 17571. 



^Analysis by J. P. Maider, City Chemist of Spokane, made at the instance of 

 Mr. Henry Fair and kindly furnished by Mr. L. P. Gratacap of the American 

 Museum of Natural History of New York; the sp. gr. determination is by Mr. 

 Gratacap, and the optical data by E. S. L. 



c Hutchinson, loc. cit. 



d Ortloff, loc. cit. 



e This value must be in error as pointed out above. 



occurrence will be described in a forthcoming number of the 

 American Mineralogist. The probable error in the indices of 

 refraction for these two new measurements does not exceed 

 ±0.005. 



