118 B. T. Hill — Hematite and Martite of Mexico. 



acteristic Comanche species. The latter author also publishes 

 a map of Jalisco, in which the eruptive rocks in the vicinity 

 of these mines are for the most part called dioritic* 



Sinaloa. — Prof. Silliman, in the valuable paper referred to, 

 describes several occurrences of martite in Sinaloa. Almost 

 nothing is known of the general geology of this State, but 

 from the descriptions given of the ores at Tepuche, Bescuino 

 and Cosolu, the conditions seem similar to those of Durango 

 and Monclova. He says that the iron of Tepuche "occurs in 

 a porphyry resembling that of the Sierra de Mercado '' (of 

 Durango), and that those of Cosolu are surrounded by calcare- 

 ous rocks. The localities also yield magnetite. 



Hidalgo, Mihoacan, Queretaro, Zacatecas and San Luis. — 

 There are many references to ores in these States in the Mexi- 

 can geological literature, which lead to the inference that they 

 are of the same character as those we have described. In 

 Queretaro, Barcena mentions the occurrence of a hematite 

 which he "believes is contemporaneous with the porphyry." 

 He also describes the occurrence of hematite associated with 

 tin in a Tertiary porphyry in the Meza de los Caballos of 

 Zacatecas. In Hidalgo he says there are large beds of hema- 

 tite, mixed with magnetite, in the post-Cretaceous formations. 

 He refers to many other localities in the States of Jalisca, 

 Durango and Mihoacan, and says that these ores constitute the 

 chief deposits of iron in the republic. f Virlet;}: mentions the 

 occurrence of iron ore at the contact of limestone and diorite 

 in the eastern Sierra Mad res, in the State of San Luis. 



Guerrero. — One of the most interesting descriptions of iron 

 ore in Mexico is that given by Manross in this Journal for 

 May, 1865. He mentions eight localities of the occurrence of 

 iron ore in Guerrero, which, with the exception of his age 

 determinations, greatly resemble the Monclova and Durango 

 deposits. " The first of these is situated at a distance of four 

 miles from Mescala. It is a vein twenty five feet wide and 

 nearly vertical, and consists of solid magnetite ore." Another 

 is " three hundred feet high, half a mile long and fully one- 

 third of its bulk is pure magnetic ore." It "contains a bed of 

 limestone at its summit." Another is four hundred yards 

 long and one hundred yards wide. The unfortunate death of 

 this young student renders it impossible to ascertain further 

 data from him concerning the ores. At the time he wrote his 



* Ensavo Estadistico del Estado de Jalisco, etc, por Mariano Barcena. Mexico, 

 1891. 



f These notes are taken from various observations following the mineral de- 

 scriptions in Barcena's " Tratado," already quoted. Other notes on iron are 

 found in his various statistical essays on the separate States of Mexico. 



% Coup d'ceil general de la topographie et la geologie du Mexique, etc., par M. 

 Virlet d'Aoust, Bull. Soc. Geologique de France. 1866. 



