. SiUi ',,,,,!,.— /,>,,„ Ore of Mexia 



1. Cerro de Mercado. 

 f specimens from the famous Iron Mou 

 of Durango has lately been placed in i 

 P. North, Engineer of the Sinaloa anc 

 panj, who obtained them, last year, in the discharge of his 

 professional duties. At first sight the octahedral crystals of very 

 various size suggested only magnetite, but the magnet tailed 

 to attract the ore, while the streak immediately indicated 

 hematite, and left no reasonable doubt that the whole mass 



Fortunately, Mr. John Birkinbine, Engineer, of Philadelphia, 



had the goodness, about the time I received Mr. North's collec- 

 tions, to send me his " Report upon the Iron Mountain of 

 Durango," of date March, 1882, from which I glean some facts 



winch are of interest to mineralogists respecting this remarkable 



The Cerro de Mercado rises abruptly from the plains on 

 which stands the city of Durango, about one and a half 

 miles to the north of the city. This hill is one mile long, a 

 third of a mile wide, and from four hundred to six hundred 

 feet high. Mr. Birkinbine dues not confirm the statement of 

 *>ine observers that this deposit is a solid mass of iron ore. 



'He surface of the hill, indeed, everywhere exposes masses of 

 I' 1 '- which appear to be derived from one or more immense 

 beds, or veins, of specular iron standing nearly vertical, the 

 fragments of which form a talus on the slopes of the mountain 

 a 1 completely the enclosing walls of rock. From sam- 

 ples of the country rock which I find in Mr. North's collection, 

 '■■;-■ walls are of purple porphyry. Mr. Birkinbine finds 



Judications that the deposit is not all above ground, but 

 extends far beneath the plain from which it projects." The 

 ^nkinn- view of tit*: bold escarpment and (dill's of this mount- 

 ;,!l1 which accompanies Mr. Birkinbine's paper is by his 

 Courtesy reproduced herewith. 



In the collection from Mr. North I find the crystals of 

 ""irtiteof. all sizes, from those measuring more than one inch 

 on the side to druses of two to three millimeters. They are 

 a!' simple crystals, the larger ones dull, sometimes iridescent, 

 the smaller lustrous and quite black. There are no isolated 

 ke those found in the original locality described by 

 fe pix and Martius, and mentioned, with other Brazilian locali- 



