Apatite Bearing Rocks. 219 



river, and the Crown Hill and High Eock mines on the west 

 side. At the Little Eapid mine the dyke carrying the apatite 

 cuts the surrounding well banded gneiss at an angle of thirty 

 degrees, while on the ridge to the south another large dyke 

 of fifty feet or more in breadth cuts the stratified rock at 

 an even greater angle. At the North Star mine, the strike 

 of the principal dyke is nearly with that of the gneiss, but 

 in the most southerly pit, the gneiss has been heaved up 

 and bent round a portion of the dyke, the contact of the two 

 kinds of rock being very sharply defined. At the London 

 and Philadelphia mines the intersections of the pyroxene 

 across the strike are well shown, as also at the High Rock 

 workings, where there is sometimes a perfect net work of 

 dykes of different kinds, small masses of the stratified 

 gneiss being enclosed in the intrusions. It may be re- 

 marked that at all these mines the country rock is banded 

 gneiss of the greyish quartzose variety, or what we regard 

 as the sedimentary portion which underlies the crystalline 

 limestone formation. 



At the Crown Hill, in the pit on the west side of the 

 main ridge, the capping of the gneiss upon a portion of the 

 pyroxene is well seen, the mass of the dyke being exposed 

 at the surface of the hill, a short distance further east. 



As regards the manner in which the apatite occurs in the 

 pyroxene, it may be said that in nearly every case through- 

 out the entire mining district the phosphate is found in 

 that portion of the dyke contiguous to the surrounding 

 gneiss. In certain large dykes as at the North Star it was 

 found along both margins of the intrusion. In some cases 

 a certain amount of regularity in its distribution was ob- 

 served for a short distance, but this waR not long main- 

 tained. Frequent branches or spurs are given off into the 

 surrounding pyroxene, and the deposits as a whole are ex- 

 ceedingly irregular, sometimes opening out into great 

 masses of several hundreds of tons, while at others they 

 dwindle down to mere strings, which cannot be profitably 

 extracted. The central portion of the dykes are for the 

 most part barren. No defined foot-wall can be observed, 



