222 N - YAM AS AK I. 



Occurrences of piedmontite as the secondary constituent of 

 eruptive rocks have been noticed by only few petrographers.* 

 Recently, this mineral was specially mentioned by late Gr. H. 

 Williams as a component of the ancient rhyolite of the South 

 Mountain. f The mode of occurrence and the mineralogical properties 

 of it are nearly the same as those of the Shinano specimen. The 

 only difference between them is in their colour. The piedmontite of 

 the South Mountain rhyolite is of a deep colour, as usual, while the 

 colour of this rhyolite is light. 



I have to express my warmest thanks to Prof. B. Koto for the 

 valuable advice which he has Oliven me during: this work. 



* Th. Liebisch found it in the red porphyrite of Egypt. Zeitschr., d. d. geol. Ges., 

 vol. XXIX, p. 717, 1877. E. Haworth mentioned its presence in a porphyrite of Missouri, 

 American Geologist, vol. I, p. 365, 1888. See also Johns Hopkins Univ. Circ, April number, 

 1883. J. P. Iddings noted its occurrence in the augite border around quartz-grains in a basalt 

 from Nevada. Geology of the Fureka District, Nevada, Appendix B, p. 393. 



t G. H. Williams, Piedmontite and Scheelite from the ancient rhyolite of South Mountain 

 Pennsylvania. Am. Jour. Sei., vol. XLVI, p. 50, 1893. 



