186 0. A. Derby- Gold-bearing Lodi oj Passagem. 



mineralized portion of the lode. The occurrence (see fig. -J), 

 in the broken-down material, of pieces of stratified quartzite 

 shows that the wall of the drift must he in close proximity to 

 the contact of the lode with the country rock, although the 

 plane of contact is not vet clearly exposed in the working. 

 This circumstance suggests that the inclusions may possibly 

 represent a contact mineral developed locally in the marginal 

 zone of the lode, rather than an original constituent, but for 

 the purpose of the present study this question is immaterial. 



The accompanying figures present, about half natural size, 

 four of the most significant slabs of the lode rock that came to 



Fig. 1. 



hand. No 1 is a mass of typical glassy vein quartz studded 

 with inclusions which in part show sharp cut crystalline out- 

 lines, while fig. 2 shows a corresponding part in the central 

 zone (B), flanked on one side by a zone (A) of country rock 

 and on the other by a zone (C) of highly tourmalinized quartz 

 with a certain admixture of pyrites. 



The inclusions consist of sericitic mica, in place quite 

 coarsely crystalline, in milky white flakes (as in the central and 

 left portions of the one at the middle of the lower border of 

 fig. 1), but for the part in cryptocrystalline masses of a light 

 greenish color. In places the characteristic luster and cleav- 

 age of an original feldspathic mineral are preserved, but for 



