296 JOSEPH STRUTHERS 



sent to Chihuahua, and their mineralogical character deter- 

 mined. Mr. George W. Wanless, of the Rio Grande Smelt- 

 ing works, and Mr. Charles Allen, of Socorro, N. Mex., under 

 the direction of the Mexicans, found the veins and located 

 the first mineral claims. Shortly after this Prof. Wilham 

 P. Blake described these deposits under the title Cinnabar in 

 Texas, the first important article concerning this subject on 

 record. Considerable prospecting work was carried on in 

 the district, but it was not until 1898 that the metal was 

 produced in commercial quantities. 



The deposits of cinnabar at Terlingua are of two classes; 

 one occurs in hard and durable limestone and the other in 

 soft and friable argillaceous beds. The ores are cinnabar, 

 mercury, yellow sulphide, and terlinguaite, and contain in 

 addition several other mercury minerals, such as calomel, 

 eglestonite, and montroydite, which, on account of their 

 rarity, are of scientific interest only. Cinnabar is the prin- 

 cipal mineral and is usually mixed with clay or iron oxide. 

 Native mercury is present in several localities in the district, 

 occurring in the interstices of crystalline calcite, and a single 

 cavity in the calcite veins has yielded as much as 20 pounds 

 of the native metal. The associated gangue is composed 

 of calcite, aragonite, gypsum, and occasionally a little barite ; 

 iron oxide, pyrite, and occasionally arsenic and manganese 

 minerals. 



