24 Van Horn — Silver, Copper, and Cobalt Minerals. 



the mines of the region, may be found in the papers previously 

 cited. 



Minerals Occurring at Veta Mica Mine and Elsewhere in ijxe 



District. 



The writer has been able to identify 21 different minerals 

 in the ores and veinstones of the Yeta Rica mine. These are 

 grouped according to the arrangement of Dana's System of 

 Mineralogy as follows : 



Native Elements — Sulphur, silver, copper. 



Sulphides — Argentite, galena, chalcocite, covellite, chalcopyrite. 



Sulpho-salts — Proustite, pearceite. 



Haloids — Cerargyrite var. embolite. 



Oxides — Cuprite, hematite, limonite. 



Carbonates — Calcite, cerussite, malachite, azurite. 



Arsenates — Erythrite. 



Sulphates — Barite, gypsum. 



In addition to these, Mr. Cochran in a personal communica- 

 tion vouches for the presence of sphalerite in small amounts. 

 Chism* mentions in the district among others, pyrolusite, 

 psilomelane, quartz, silver chloride, and lead sulphate ; and 

 Malcolmsonf speaks of the presence of " copper oxide," and 

 " zinc carbonate." In all, it would seem that 28 minerals 

 have been identified from Sierra Mojada up to the present 

 time. Of these, eight have never been mentioned by any one 

 except the present author, and, therefore, may certainly be 

 claimed as new occurrences. These minerals are as follows : 

 copper, calcite, malachite, chalcocite, covellite, proustite, pearce- 

 ite, and erythrite. There is also some uncertainty as to 

 whether embolite and cuprite have been previously recog- 

 nized, although Chism speaks of the presence of silver bromide 

 in small amounts, and Malcolmson mentions copper oxide with- 

 out further specifying whether it is cuprite or tenorite. 



Description of Minerals found at Veta Rica Mine. 



Because of the fact that nothing has been observed in miner- 

 alogies concerning Sierra Mojada, it has seemed advisable to 

 give a short description of the occurrence of the minerals from 

 the Yeta Rica mine which have been determined by the writer. 

 One interesting feature of the specimens is the almost univer- 

 sal presence of gypsum as a gangue mineral. Barite is nearly 

 as common, whereas quartz was not identified, and calcite was 

 found in but few places. 



* Op. cit., page 550. f Op. cit., pages 107 and 131. 



