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cordant stratification a blackish blue slate 

 very fissile, and traversed by small veins of 

 quartz. The green slates include some strata of 

 gruenstein, and they even contain balls of this 

 substance. I nowhere saw the green slates 

 alternate with the black slates of the ravine of 

 Piedras Azules ; at the line of junction, these 

 two slates appear rather to pass one into the 

 other, the green slates becoming of a pearl-gray 

 in proportion as they lose their hornblende. 



Farther South, toward Parapara and Ortiz, 

 the slates disappear. They are concealed under 

 a trap formation more varied in it's aspect. 

 The soil becomes more fertile ; the rocky masses 

 alternate with strata of clay, which appear to be 

 produced by the decomposition of the gruen- 

 steins, the amygdaloids and the phonolites. 



The gruenstein, which farther North was less 

 granulous, and passed into sespentine, here 

 assumes a very different character. It contains 

 balls of mandelstein, or amygdaloid, of eight or 

 ten inches diameter. These balls, sometimes a 

 little flattened, are divided into concentric layers. 

 This is the effect of decomposition. The nucleus 

 is almost as hard as basalt. They are inter- 

 mingled with little cavities, owing to bubbles 



* The two formations of green and blackish blue slates 

 are directed N. 52° E. (or hor. 3-4), and dip 70° N. W* 



