CONTRIBUTIONS FROM THE HARVARD MINER ALOGICAL 



MUSEUM. — XIII. 



NOTES ON THE CRYSTALLOGRAPHY OF LEADHILLITE. 



By C. Palache and L. La Forge. 



I. LEADHILLITE FROM UTAH. 



Presented December 9, 1908. Received January 14, 1909. 



The crystals of leadhillite described in this paper were found and 

 sent to the Harvard Mineralogical Museum for identification and study 

 by A. F. Holden, then of Salt Lake City, in 1897. The writers desire 

 to express here their thanks to Mr. Holden for so generously placing 

 this rare material in their hands for investigation. 



The leadhillite was found in the Eureka Hill Mine, Tintic Mining 

 District, Utah, at a depth of 500 feet. It occurred in a few cavities in 

 massive galena which are coated with quartz and anglesite, upon which 

 the leadhillite is implanted. Of its occurrence Mr. Holden writes that 

 it seems to appear only where the galena is impure, anglesite being the 

 sole alteration product where the galena is free from impurities. The 

 anglesite is both massive and in small clear colorless crystals, elongated 

 parallel to the b axis and showing the forms c (001), b (010), m (110), 

 1 (104), o (011), and y (122), the latter form dominant. 



So far as known to us the material sent us is all that was found. 1 

 It consists of several loose crystals of rhombohedral appearance and 

 dull lustre, semitransparent, and of several pieces of massive galena 

 with leadhillite crystals still attached to the walls. The latter crystals 

 are transparent, of a faintly yellowish white color and adamantine lus- 

 tre. They are mostly tabular, half an inch or less across, and upwards 

 of an eighth of an inch thick. The most prominent characteristic by 

 which they may certainly be distinguished from the accompanying 



1 In " Utah Minerals and Localities," Maynard Bixby, Salt Lake City, 

 1904, the occurrence of leadhillite in the Tintic District is described as fol- 

 lows: "Leadhillite has been observed rarely, but the crystals seen were of 

 good quality, nearly colorless, and averaged possibly more than a half inch 

 across." This is the only published reference to this occurrence. 



