Mineralogy of South America. 143 



currence of lodes are known, still the greater part of the gold 

 is obtained and larger workings are carried on in the bed of the 

 river itself during the dry season of the year. It is well known in 

 commerce, however, that the gold from the whole of this district 

 is extremely inferior to that of the districts further north, before 

 referred to. It has a much less noble appearance, a smaller 

 specific gravity, and contains a greater quantity of silver. A 

 specimen from the washings carried on by SS. Gove et C le was 

 examined, and afforded the following results. 



The specific gravity was taken on two separate quantities of 

 small pepites, size of from that of a small linseed to that of a 

 melon-seed. 



a. Specific gravity taken on 107*19 grs. gave 16*54 at 60° F. 



b. Specific gravity taken on 119*12 grs. gave 1663. 

 On analysis the results were respectively — 



Gold .... 78*695 79*89 



Silver . . . 21*305 20*11 



100000 100*00 



Another specimen of still lighter colour gave a specific gra- 

 vity of 15*83, but was not analyzed. 



Gold from the River Chuquiaguillo. — This river, which flows 

 into the river of La Pay immediately below that city, had been 

 worked before the Spanish conquest from time immemorial by 

 the Aymara Indians, and the gold obtained has been entirely 

 due to the operations carried on for washing the bed of the river, 

 as described in the Report to the Geological Society of London*. 

 The gold obtained from these washings varies greatly in quality, 

 but in general is of very inferior quality. The proprietor of the 

 most extensive workings, Don Pedro Saiemtz, kindly presented 

 me with the largest nugget which he had obtained, and which 

 weighed 432 grs. 



Its specific gravity at 60° Fahr. was found to be 16*693, and 

 a chemical examination gave its composition as consisting of — 



Gold 90*86 



Silver 914 



10000 



Native Silver from Chuquiaguillo. —Along with the above spe- 

 cimen of gold I received another nugget from the same locality, 

 which was supposed to be native platinum f, but on examination 



* Communicated November 21, I8f>0: see Quart. Journ.Geol. Soc. 1861. 



t I may here mention that although platinum is frequently said to occur in 

 Bolivia, and on the late map of that country by Ondorza and Mujica very 

 many localities of platinum are marked, I never succeeded whilst there 

 in procuring any reliable evidence of its existing, or even ever having been 

 found in that country. 



