Dec, 1908. 



MlNERALOGICAL NOTES 



139 



account of calamine,* of a habit quite similar to the above and 

 also from a Maid of Erin mine. The occurrence described by Pratt 

 is, however, in Clear Creek Co., Colorado, while the 

 locality here represented is in Lake Co. As the crys- 

 tals prove upon examination to exhibit a development 

 somewhat different from that described by Pratt, 

 there seems little doubt that they represent a separate 

 occurrence. Inquiry by the writer of the company 

 now operating the mine from which the Leadville 

 calamine was stated to have come, elicited the infor- 

 mation that some of the v/orkmen thought that such 

 crystals had been obtained in earlier operations at 

 the mine but none was being found at the present 

 time. The company also forwarded a specimen quite 

 similar to the one above mentioned, with the informa- 

 tion that it had been found at the El Paso mine 

 adjoining. 



Like the Clear Creek Co. calamine, the Leadville 

 crystals are tabular with respect to b (010) and con- 

 siderably striated in the prismatic zone. They are, 

 however, differently terminated. Most commonly 

 the termination is the unit macrodome 5 (101). 

 Occasionally, however, the steeper dome t (301) is to 

 be seen and the unit brachydome probably also occurs although this 

 could not be verified. The usual appearance of the crystals is illus- 

 trated in the accompanying Fig. 1. Occasionally there is a larger 

 development of the prism, giving a stouter form. The crystals tend 

 to form groups which are partly radiated and partly joined by the 

 brachy-pinacoid. No doubly terminated crystals were found, so 

 that no opportunity was afforded for a study of the hemimorphic char- 

 acters of this mineral. Gentle heating causes the crystals to become 

 strongly electric. The character of the electricity developed by such 

 heating was tested in the following manner : Numerous crystals were 

 suspended by silk threads and after heating, glass rods electrified by 

 silk or sealing wax excited by flannel were brought near. In every 

 case the positively electrified substance, i. e., the glass, attracted the 

 terminated end of the crystal and the negatively electrified, the broken 

 end. The average length of the crystals is about 10 mm. They are 

 transparent to translucent and colorless to white. The faces best 

 suited for measurement are the macrodomes, an especially sharp 



* Am. Jour. Sci., 1894, 3, 48, p. 213. 



Fig. 



Calamine. 



