1910.] NATURAL SCIENCES OF PHILADELPHIA. 539 



Several samples of stilbite were found as thin radiating layers of 

 crystals upon the face of the rock. These crystals readily broke into 

 flat pearly plates. They gave much water when heated in a closed 

 tube and were decomposed by hydrochloric acid without the forma- 

 tion of a jelly. Before the blow -pipe they fused with swelling and 

 intumescence to a white enamel. The specific gravity was found to 

 be 2.12. Upon analysis there were found: 



SiO, .' 54. 27 per cent. 



A1,0 3 17.24 



CaO 7.81 



Na,0 1.81 



Igi{ 19.56 



Garnets, varying in color from black to green, brown to gray, trans- 

 parent in thin sections with a greenish to brownish tint, were observed 

 distributed through the rocks. The specimen analyzed showed a 

 specific gravity of 3.6, and upon anabysis gave: 



SiO, 34.98 per cent. 



Fe 2 6 3 26.82 



FeO 0.37 



AL0 3 5.82 



MnO 0.08 " 



CaO 31.23 



MgO 0.57 



Pyroxene. — This appeared in light green colored crystals with a 



violet lustre. It fused quietly but with difficulty to a brown glass. 



It was insoluble in hydrochloric acid. The crystals showed the 



outward form of the hexagonal system. The specific gravity of the 



specimen analyzed was found to be 3,187. Its analysis showed: 



SiO, 52.23 per cent. 



A1.0, 3.58 



FeO 2.45 



MnO 1.55 



CaO 20.00 



MgO '. 18.31 



Ign 1.79 



Chabazite. — The crystals were colorless or white. When heated 

 in a closed tube they gave out much water. They were decomposed 

 by lwdrochloric acid without the formation of a jelly. They fused 

 before the blow-pipe to a plebby glass. The specific gravity was 

 found to be 2,053. The analysis showed: 



Si0 2 48.59 per cent. 



A1 2 3 18.49 " 



CaO 8.78 



MgO 0.05 



-\a,0 1.41 " 



K,0 0.69 " 



Ign 22.01 



