1869.] TATE GTJYAIfA, IN YE]S^ZUELA. 345 



the thickness is very considerable, and the area undoubtedly great. 

 The dip and strike of the rocks are given with reference to the 

 magnetic meridian. The sequence of the various rocks can be made 

 out with tolerable precision ; on the whole the felspar predominates 

 in the lower strata, whilst hornblende and mica increase in quantity 

 as we rise in the series*. 



1. Felstone and Talcose Schists. — To the extreme south of the line 

 of section, and beyond the river Yuruari, is situated the Caratal 

 gold-field, which until the last ten years remained hidden in the soli- 

 tude of the virgin forest. The auriferous veins are included chiefly 

 in a felstone, "piedra azul" of the miners, and also in a talcose schist. 

 From the usual mode of association of auriferous veins with diorites 

 in Central America and Bolivia, I was led at first to regard the 

 chief auriferous rock of the Caratal gold-field as a diorite in which 

 the hornblendic constituent was wanting; but its immediate associa- 

 tion with the talc-schist, and its conformity with the metamorphic 

 series of the country, have finally induced me to view it as consti- 

 tuting a part thereof. Unfortunately, the absence of sections has 

 prevented my satisfying myself on this point ; but one section on the 

 Eio Mucupio exhibits the talc-schists overlying the felstone, dipping 

 together to the north at from 60°-70°, and striking west 30° north : 

 there are no evidences of alteration along the line of junction ; and 

 elsewhere the talcose rock appears incorporated with the felstone. 



The felstone is homogeneous, of close texture, and usually semi- 

 columnar ; but where it constitutes the vein-stone of the Tigre and 

 Santa-Maria lodes, it contains isolated quartz-crystals and chlorite. 

 To the south-west of ISTueva Providencia and high up on the river 

 Yguana the strike approaches north and south, and the dip is 

 85°-90° westerly. 



2. Caratal Gold-field. — The auriferous area at present known is 

 about twelve square miles, the whole of which is traversed by 

 gold-bearing quartz-veins, averaging in thickness from 2-3 feet, 

 most of which have yielded visible gold in abundance. The richness 

 of some of the lodes, and of the "placer" diggings of this auriferous 

 tract, fully justifies the appellation of " El Dorado " which has been 

 given to it ; and it may be the " El Dorado " that incited Raleigh to 

 penetrate Venezuela, but which he failed to discover. 



The veins present little conformity as regards their strike ; but 

 many apparently trend about N.E. and S.W. ; the dip varies from 

 45°-90°. I have obtained gold in the felstone and talc-slates, in 

 the vicinity of the auriferous lodes ; but it has not occurred to me 

 disseminated in the main masses of these rocks. Great diversity in 

 the character of the quartz prevails, so much so that specimens from 

 the various lodes can in the majority of cases be readily identified, 

 as, for instance, that of the Callao lode is highly vitreous, with the 

 gold more or less lamelliform and arborescent ; that of the Potosi 

 lode is saccharoid, with finely disseminated gold, and granular gold 

 localized in the parallel strings of hsematite, which also are rich in 



* [Specimens of rocks and minerals, in illustration of this paper, have been 

 presented by the Author to the Society. — Edit.] 



