38 The Phosphates of America. 



spathic rock, the pyroxenite and the apatite, as are also many 

 smaller quartzo-feldspathic veins, which, both here and in other 

 localities in this region, intersect at various angles the apatite, the 

 pyroxenite and the granitoid rock into which the latter graduates. 

 We have thus included in these great apatite-bearing lodes 

 quartzo-feldspathic rocks of at least two ages, both younger than 

 the enclosing gneiss. A smaller vertical vein of fine-grained black 

 diabase-like rock intersects the whole. No one looking for the 

 first time at this section of forty feet, as exposed in the quarry, 

 with its distinctly banded and alternating layers of pyroxenite 

 and granitoid quartzo-feldspathic rock, including two larger and 

 several smaller layers of crystalline apatite, would question the 

 stratiform character of the mass, whose venous and endogenous 

 nature is nevertheless distinctly apparent on further study. 



In other portions of the same great vein, quarried at many 

 points, this regularity of arrangement is less evident. Occasion- 

 ally masses are met with presenting a concretionary structure, and 

 consisting of rounded or oval aggregates of orthoclase and quartz, 

 with small crystals of pyroxene around and between them ; 

 the arrangement of the elements presenting a radiated and zone- 

 like structure, and recalling the orbicular diorite of Corsica. 

 The diameter of these granitic concretions varies from half an 

 inch to one and two inches, and they have been seen in several 

 localities in the veins of this region over areas of many square 

 feet. 



In the Emerald mine the stratiform arrangement in the vein is 

 remarkably displayed. Here, in the midst of a great breadth of 

 apatite, were seen two parallel bands (since removed in mining) of 

 pyroxenic rock, several yards in length, running with the strike of 

 the vein, and in their broadest parts three and eight feet wide re- 

 spectively, but becoming attenuated at either end and disappear- 

 ing, one after the other, in length, as they did also in depth. These 

 included vertical layers, evidently of contemporaneous origin with 

 the enclosing apatite, were themselves banded with green and 

 white from alternations of pyroxene of a feldspar with quartz. 

 Accompanying the apatite in this mine are also bands of irregular 

 masses of flesh-red calcite, sometimes two or three feet in breadth, 

 including crystals of apatite, and others of dark-green amphibole. 

 Elsewhere, as at the High Rock mine, tremolite is met with. In 

 portions of the vein at the Emerald mine pyrite is found in con- 

 siderable quantity, and occasionally forms layers many inches in 



