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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 gruensteins, 

 the amygdaloids, and the phonolites. 



The gruenstein, which farther North was less 

 granulous, and passed into serpentine, 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. 



