W. M. Bradley — New Silver- Tellurium Mineral. 163 



Zonal Assignment of the Nodule Bed. — Whether the 

 Lawrence shales shall still continue to be regarded as unfossil- 

 iferous will depend on the disposition made of the beds 

 described above. They record the beginning of the end of 

 marine sedimentation and are followed by non-marine deposits. 

 Lithically they belong to the Lawrence shales. Faunally they 

 are related to the Kickapoo limestone ; but since lithology is 

 the chief basis for the division of the Pennsylvania!! of Kansas 

 it would seem that their reference to the shale formation 

 would be the more logical, and such an assignment is made. 



University of Kansas, June, 1914. 



Art. XV. — Empressite, a New Silver-Tellurium Mineral 

 from Colorado ; by W. M. Bradley. 



Some years ago, what appeared to be a new mineral was 

 found in the Empress-Josephine Mine in the Kerber Creek 

 District of Colorado by Professor R. D. George of the Uni- 

 versity of Colorado. No analyses were made at that time, but 

 qualitative tests were obtained which showed the presence of 

 silver and tellurium. Several small specimens were recently 

 sent to the writer for investigation. They were all massive in 

 structure, careful inquiries having failed to locate any material 

 showing crystal faces. The mineral occurs in very fine granu- 

 lar and compact masses associated with galena and native tel- 

 lurium. It is metallic in luster, and gives a grayish black to 

 black streak. The fracture is finely conchoidal to uneven, 

 and upon such surfaces the color is a pale bronze. The min- 

 eral is brittle to friable, and has a hardness between 3 and 3*5. 

 The specific gravity was determined as 7*510. In the oxidiz- 

 ing flame on charcoal it fuses at 1 giving "a heavy white coat- 

 ing of tellurium dioxide and a black globule, which if placed 

 in the reducing flame gives on cooling white dendritic points 

 of silver on its surface. Prolonged heating in the oxidizing 

 flame gives a globule of silver. In the open tube a faint white 

 sublimate of tellurium dioxide is formed which if strongly 

 ignited fuses to colorless globules. The mineral is readily 

 soluble in hot dilute nitric acid. 



The specimen selected for analysis was examined under a 

 microscope and was found to contain several very minute 

 jseams of non-metallic mineral matter which was practically all 

 removed by crushing the specimen to very fine grains and 



