abstracts: mineralogy 521 



occurs in association with the Mesozoic granular acidic intrusives and 

 in part with the Paleozoic sedimentary rocks. It is probably of early 

 Cretaceous age, is referred to the late Mesozoic epoch of metallization, 

 and was formed at considerable depth. 



The younger group of deposits occurs in or associated with the Ter- 

 tiarj^ effusive volcanic rocks, notably the rhyolite and andesite. It is 

 regarded as of late Miocene age and belonging to the late Tertiary 

 epoch of metallization. This great group in general consists of gold- 

 silver-bearing quartz veins. F. C. S. 



MINERALOGY. — The microspectroscope in viineralogy . Edgar T. 

 Wherry. Smithsonian Miscellaneous Collections, 65^: 1-16. 

 1915. 



Previous work with the microspectroscope having been limited to 

 a very few minerals, observations have been made on a number of 

 additional ones. The most convenient apparatus is a binocular micro- 

 scope with an Abbe-Zeiss Spectral-Ocular. Light is best obtained 

 from a Welsbach burner or Nernst lamp, and is concentrated laterally 

 on the specimens, the wave lengths of the absorption bands being read 

 off on a scale. The method is of considerable practical value in the 

 identification of certain colored minerals, and in particular of cut gems. 



Most of the rare-earth minerals show two or more bands, which are 

 useful in distinguishing these minerals from all others, and to some 

 extent in differentiating individual species. Violet calcite from Joplin, 

 Missouri, shows bands which indicate that its color is due to the pres- 

 ence, in mix-crystal form, of a carbonate of neodymium. Some minerals 

 containing uranic uranium show characteristic bands, while zircon, 

 containing this element in the uranous form, exhibits a different set 

 of bands. The colors of the various members of the garnet group have 

 been ascribed to several elements, but it is shown by tabulating the 

 colors, spectra, and percentages of chromium, vanadium, and man- 

 ganese for six different specimens that the colors are due chiefly to the 

 first two of these elements. 



Tables are given of the spectra of rare-earth minerals, uranium 

 minerals, and minerals with red, yellow, green, blue, and violet colors; 

 a determinative table for minerals showing bands of sufficient intensity 

 for diagnostic purposes; and finally a table of the elements producing 

 absorption spectra, with their forms and the limits to the amounts 

 present. E. T. W. 



