468 Hidden and Pratt — Associated Minerals of Rhodolite. 



One-half mile due north of the rhodolite placer mine, near 

 the summit of Mason Mountain, a ledge of rock is exposed, 

 which is composed almost entirely of impure rhodolite and 

 biotite, with a very considerable quantity of the iron sulphides 

 disseminated through them. Sperrylite has been obtained by 

 panning the sands naturally concentrated in the crevices and 

 cavities weathered in the ledge, which would seem to indicate 

 that this ledge is one of the original sources, if not the source, 

 of the sperrylite found in the valley below. 



In conclusion the authors, wish to express their thanks to 

 Prof. S. L. Penfield of the Sheffield Scientific School for his 

 kindness in making many tests to positively identify the min- 

 erals herein described. 



September, 3 898. 



