THE HOltROS OF SAN JUAN. 
77 
faining veins of copper-ore* At the foot of this mountain 
two fine springs gush out from the serpentine. Near the 
village of San Juan, the granular diabasis appeal’s alone 
uncovered, and takes a greenish black hue. The feldspar 
intimately mixed with the mass, may be separated into 
distinct crystals. The mica is very rare, and there is no 
tpiartz:. The mass assumes at the surface a yellowish crust 
like dolerite and basalt. 
In the midst of this tract of trap-formation, the Morros 
oi San Juan rise like two castles in ruins. They appear 
linked to the monies of St Sebastian, and to La Galera 
v Inch bounds the Llanos like a rocky w all. The Morros of 
ban J uan are formed of limestone of a crystalline texture ; 
sometimes very compact, sometimes spongy, of a greenish- 
grey, sliming, composed of small grains, and mixed with 
scattered spangles of mica. This limestone yields a strong 
effervescence with acids. 1 could not find in it any vestige 
o organized bodies. It contains in subordinate strata, 
masses ot hardened clay of a blackish blue, and carburetted. 
ifiese masses lire fissile, very heavy, and loaded with 
iron ; their streak is whitish, and they produce no efferves- 
cence with acids. They assume at them surface, by their 
decomposition in the air, a yellow colour. We seem to 
recogmze in these argillaceous strata a tendency either 
iasneri trS 10 "*!’ 0r , to the ^sehchiefer (schistose 
T cWa f f: ™ e the black transition- 
limestones. When m fragments, they might betaken at 
hast sight for basalt or hornblende.+ Another white lino 
baTs’theTrf’ “«* SenSsfe; 
i,^ J r Sa , U Ju ; m - 1 could n ° fc see line of 
’faSnidS SJ™ “ t0 ” 8 ' ” « f *'» 
where' it ^ ^ seTpe’ntke! 
pernendie,ilarf ratlfi i d SOme re S uiarit y> run hor. 8, and dip almost 
where if- ^ found malachite disseminated in this serpentine, 
t I h PaSS6S mt ° SrUnstein. 
rocks of s. an T 0pp0rt 1 nity °* exa mining again, with the greatest care, the 
s t av , t D ^ uan » °* ^Jhacao, of Parapara, and of Calabozo, during my 
-lmniiUnwf IU: °’i w '’f re * conjointly with M. del Rio, one of the most dis. 
ieetion for Pr i° f . th j schoo! of Freyberg, I formed a geognostical coi 
011 tor lhc Colegio de Miaeria of New Spain. 
