THE MOllEOS or SAN JUAN. 
387 
■quartz; its mass is formed of small crystals of felspar, 
intermixed with crystals of amphibole. This rock of diorite 
is covered at its surface, by the cil'cct of deoomposition, 
with a yellowish crust, like 'that of basalts and dolerites. 
■Serpentine, of a dull olive-green and smootli fracture, mixed 
with bluish steatite and amphibole, in’cseiits, like almost all 
the co-ordinate formations of diorite and serpentine (in 
■Silesia, at Fichtelgebirge, in the valley of Baigorry, in the 
Pyrenees, in the island of Cyprus, and in the Copper Moun- 
tains of circumpolar America),* traces of copper. Where 
the diorite, partly globular, approaches the green slate of 
Malpasso, real beds of green slate are found inclosed in 
diorite. The fine saussurite which we saw in the Upper 
■Orinoco in the hands of the Indians, seems to indicate the 
existence of a soil of cuphotide, superposed on gneiss- 
granite, or amphibolic slate, in the eastern part oi the Sierra 
Parime. 
IV Geanular and micaceous Limestone of the 
Moreos of San Juan.— The Morros of San Juan rise like 
ruinous towers in a soil of diorite. They are formed oi a 
oavenious grevish green limestone of crystalline texture, 
mixed with soilie spangles of mica, and are destitute of sheila. 
We see in them masses of hardened clay, black, tissile, 
charged 'U'itli iron, and covered ii crust, yellow from do- 
composition, like basalts and amphiholes. _ A comiiact lime- 
stone eontainiiig vestiges of shells, adjoins this granular 
limestone of the Morros of San J uan, which is hollow within. 
Probably on a further examination of the e.\traordinary strata 
■between Villa de Cura and Ortiz, of which 1 had time only 
to collect some few specimens, many phenoineiia imy ho 
discovered analogous to those which Leopold von Bnch has 
lately described in Souili Tyrol. U. Bonssmgault m a 
memoir which he has recently addressed to me, calls the 
rock of tlie Morros a “ problematic calcariferoiis gneiss. 
This expression seems to prove that the iihites of mica take 
in some parts a uniform direction, as m the grew'uisU 
dolomite of Val Toccia. 
* Franklin’s Journe* to the Polar Sea, p. 529. 
2 c 2 
