0. A. Derby — Manganese Ore Deposits of Brazil. 213 



Akt. XXII. — On the Original Type of the Manganese Ore 

 Deposits of the Queluz District, Minas Geraes, Brazil • 

 by Orville A. Deeby. 



In a paper published in the July number for 1901 of this 

 Journal, the commercial manganese ore that in recent years 

 has been quite extensively shipped from the Queluz (Lafayette) 

 district, in the state of Minas Geraes, was attributed to the 

 alteration and leaching of an original silicate rock for which 

 the name Queluzite was proposed. 



Of the various types of this rock described in that paper, 

 the only one that almost completely preserved its original ele- 

 ments consisted almost exclusively of manganese garnet (spes- 

 sartite) with a slight admixture of another silicate element, 

 usually much altered, that was referred doubtfully to the 

 amphibole group. Another consisted of spessartite with a 

 large admixture of quartz which was presumed to be secon- 

 dary, replacing some mineral, or minerals, that had entirely 

 disappeared ; while a third presented minute isolated grains of 

 spessartite distributed through a ground mass of hard steely 

 manganese oxide that had the appearance of a primary con- 

 stituent. 



Since the writing of that paper, one of the mines there 

 mentioned, that of Piquery, has been stripped of nearly all of 

 the secondarily enriched material, and has been abandoned 

 after furnishing about 250,000 tons of merchantable ore. A 

 recent hurried visit to this mine revealed some interesting and 

 unexpected features, which seem worthy of a preliminary 

 notice pending a more detailed investigation, which it is hoped 

 can soon be made. 



The bottom of the mine shows exposed in a perfectly sound 

 condition a large surface of the original rock from which the 

 merchantable ore was derived. This consists mainly of a 

 black, fine-grained, highly jointed and somewhat flaggy rock 

 with the aspect of a limestone, with broad bands and patches 

 of a more massive (less jointed), yellowish gray (where 

 unstained by secondary manganese oxide) rock with the aspect 

 of a quartzite. The latter is in part the garnet rock described 

 in the above-cited paper from an isolated mass preserved in the 

 midst of the merchantable ore, and which is now seen to con- 

 stitute segregated masses and layers which, as regards the 

 entire body of manganese-bearing rock, are of secondary 

 importance, instead of being, as supposed, the predominant 

 type of that body. This is constituted by the limestone-like 

 rock which on treatment with cold weak acid gives a brisk 



