proceedings: geological society 239 



miles. Jean, on the San Pedro, Los Angeles, and Salt Lake railroad is the 

 principal shipping point. Goodsprings, 8 miles northwest of Jean with 

 a population of 200 is the largest town. 



The ore deposits are of zinc and lead and form ver.y irregular replace- 

 ments which usually occur in more or less crystalline upper Mississippian 

 limestone. They are found thru a vertical range of 3000 feet and do not 

 seem to be restricted to any particular member of the sedimentaries. 

 The principal factors in the localization of the ore bodies appear to be 

 the presence of joints and crushed zones which in general strike east and 

 west or nearly north and south, and are in most places nearly vertical. 



The zinc and lead ores are usually closeh^ associated. The ratio of 

 zinc to lead, however, is extremely variable even in the same ore body. 

 In general, the lead content is higher in the upper part of the ore bodies. 



The only sulphide mineral common to these ores is galena. Part is 

 probably original but some is undoubtedly secondary. At one place in 

 the Potosi mine a small bod}^ of sphalerite ore was found entirely sur- 

 rounded by oxidized zinc ores. This ore is considered to represent the 

 primary ore, but it may be enriched. The sphalerite is intergrown with 

 calcite and a little galena, and is iron-bearing. 



The ores now being mined in the district consist of white or red iron- 

 stained smithsonite, with some cerussite, anglesite, and galena. Cala- 

 mine is not abundant and where seen is usually developed in the latest 

 open water-courses in the other ore. Hydrozincite is sometimes present 

 in fairly large masses in the ore bodies near the surface and often shows 

 as a white coating on the croppings. 



It is thought that the present bodies of carbonate ores have resulted 

 in part from alteration of sulphide ores in place and in part from a down- 

 ward concentration of the metals by surface waters which followed the 

 fractures in their movement towards ground- water level. 



Pre-Wisconsin drift in the region of the Glacier National Park, Montana: 

 W. C. Alden and Eugene Stebinger. An abstract of this paper was 

 published in the preliminary list of papers for the New Haven meeting 

 of the Geological Society of America. The full paper is to be published 

 in vol. 24 of the Bulletin of the Society. 



Frank L. Hess, Secretary. 



