18 0. A. Derby — Manganese Ore Deposits 



Art. II. — On the Manganese Ore Deposits of the Queluz 

 {Lafayette) District, Minas Geraes, Brazil; by Orville 

 A. Derby. 



In a communication entitled " The Manganese Ores of 

 Brazil," published in the Journal of the Iron and Steel Insti- 

 tute for the current year (1900), Mr. Herbert K. Scott gives a 

 very interesting account of two ore districts in the state of 

 Minas Geraes that within the last few years have sprung into 

 considerable prominence on account of the abundance and high 

 quality of their ores. These two districts, though adjacent, 

 differ widely in geological characters and in the mode of origin 

 of their ores. The Miguel Burnier-Ouro Preto district, which 

 is more particularly described by Mr. Scott, is constituted by a 

 series of quartzites and schists in which hematitic quartz- 

 schists (itabirites) are a prominent feature, the manganese ore 

 occurring in intimate association with these iron schists and 

 with limestone. The geological conditions are therefore simi- 

 lar to those described by Yogt in his- work iSalten og Ranen 

 for certain Norwegian deposits of associated iron and manga- 

 nese ores that have almost certainly been derived through leach- 

 ing from iron- and manganese-bearing carbonates. The de- 

 tails given by Mr. Scott are very conclusive in support of this 

 view of the mode of origin, which I have briefly discussed in a 

 note appended to his paper. 



In the closely adjacent Queluz* district, on the contrary, the 

 ore bodies occur in association with granitic and gneissic rocks 

 and there is a complete absence of the calcareous and ferrugi- 

 nous beds that accompany the ore in the other district. The 

 mining and prospecting operations thus far effected have, on 

 account of questions of transportation, been limited to a zone 

 10 to 20 kilometers wide on each side of the railroad. In the 

 zone thus defined the outcrops of ore are so numerous and 

 large as to indicate an extremely extensive and widespread 

 mineralization of an area that is doubtless much larger than 

 has thus far been recognized. The existing maps of the 

 region are so defective that no positive correlation of the dif- 

 ferent outcrops can be made, but there are strong indications 

 of the existence of at least three distinct ore belts. These are : 



1st. A western belt, marked by the two active mines of 



* The name Lafayette given in Mr. Scott's paper was given to the railway- 

 station in the border of the town of Queluz in order to avoid confusion with 

 another place of the same name in the same railway system. In common par- 

 lance the name Lafayette has come into general use for the whole district, but in 

 the administrative division of the state Queluz is still retained as the name of the 

 town and of the municipal district of which it is the center. 



