SMITHSONIAN EXPLORATIONS, 192/ 2^ 



]*klaclre occui^ies a well defined fault with schists as the foot, and 

 conglomerates as the hanging wall. 



From Guanajuato we went to Zacatecas, another of Mexico's 

 famous camps. Several large veins are found in the district, the most 

 consjMcuous l)eing the Cantera vein prominently visihle from the cen- 

 ter of the city. This vein can be easilx' followed to the south for a 

 distance of 15 kilometers ur more. The geology of this district is 

 very similar to that of Guanajuato. Mining has almost ceased in 

 Zacatecas, presumably due to the exhaustion of the bodies of com- 

 mercial ore but a number of smaller cam])s in the vicinitv have 

 promise. We visited one such district, Ojo Caliente, where the liil- 

 boa Mine attracted our attention because of the abundance here of 

 the chloro-arsenatc of lead, mimetite, and the report that other rare 

 minerals were obtainable in quantity. In fortunately the low price 

 of lead necessitated the closing of the mine a few weeks before we 

 arrived, and the exceptional material known to be still in the mine 

 was unobtainable. 



Reported new finds of fine specimens at the ()juela Mine, visited 

 during the field-work of last year, brought us there. 1 was al)le to 

 study somewhat more in detail some of the more interesting fea- 

 tures of this important deposit of lead and silver and was able to 

 collect, together with pyromorphite and other rare and l)eautiful 

 minerals, a number of good specimens of the very rare species, car- 

 minite, an arsenate of lead and iron. 



While in Mexico City we had the good fortune to arrange with 

 the officials of the Penoles Compan\ for jiermission to visit Naica, 

 in the State of Chihuahua, and take out of the famous gypsum cave 

 of the Maravilla Mine two groups of the enormous crystals that are 

 found there. The group selected for the IMuseum's exhibit consists 

 of 15 crystals, the smallest three feet, and the longest five feet in 

 length. The entire group measures ten feet in length, and will be 

 used to reconstruct a section of this unique cave. The two taken out 

 are the finest examples of large crystal groups in any Museum in the 

 world. Some smaller but very fine groups of clear gypsum were 

 also procured. 



Our next stop was at the old and famous camp of Santa Eulalia 

 where we were able by rare good luck to collect at the Potosi Mine 

 some unique specimens of ]n'rrhotite, a sulphide of iron. Single com- 

 ]:)lete individuals, two inches across and an inch thick, as well as 

 unusual matrix specimens, are lielieved to be uni)aralleled. The ore 



