THE MICROSPECTROSCOPE IN MINERALOGY 

 By EDGAR T. WHERRY 



ASSISTANT CURATOR, DIVISION OF MINERALOGY AND PETROLOGY, 

 U. S. NATIONAL MUSEUM 



The possibilities of the microspectroscope in the identification 

 of minerals and the study of their composition have apparently not 

 been generally appreciated by mineralogists. Occasional articles in 

 the journals devoted to physics and microscopy have contained 

 references to a few minerals ; three contributions to the subject from 

 a mineralogical point of view have appeared in recent years — brief 

 discussions of absorption spectra in Miers' " Mineralogy " * and in 

 Smith's " Gem-Stones " 2 and F. J. Keeley's " Microspectroscopic 

 Observations " 3 ; but in none of these is it treated as fully as might 

 be desired. The present paper comprises descriptions of the spectra 

 of a much larger number of minerals than has heretofore been 

 examined. 4 



The apparatus which has proved most satisfactory in the studies 

 here described consists of a Crouch binocular microscope stand, 

 fitted with a 37 millimeter objective, an Abbe-Zeiss " Spectral- 

 Ocular " 5 in the right hand tube, and in the other an ordinary low- 

 power eyepiece, marked on the lower lens at the point where the 

 image of a mineral grain falls when it is visible through the spectro- 

 scope slit ; the prism which diverts part of the light into the left 



1 Macmillan and Co., New York and London, 1902 ; pp. 275-276. 



2 Methuen and Co., London, 1912 ; pp. 59-62. 



3 Proc. Acad. Nat. Sci. Phila., 1911, pp. 106-116; Mr. Keeley has made a 

 number of valuable suggestions in connection with the preparation of the 

 present paper, which are herewith gratefully acknowledged. 



4 Col. Washington A. Roebling, of Trenton, N. J., kindly furnished the 

 writer with samples of a number of rare minerals from his very complete 

 collection to supplement those available at the Museum. 



5 Mr. Keeley states that he finds a Browning or Beck microspectroscope 

 ocular useful for preliminary examinations ; a Wallace grating-microspectro- 

 scope, obtained through the kindness of Mr. Thomas I. Miller, of Brooklyn, 

 N. Y., was also tried, but the spectra it yields are too faint for mineral work 

 in general. 



Smithsonian Miscellaneous Collections, Vol. 65, No. 5 



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