Brace on the Minerals of LiWifield, 351 



some emeralds in the granite. Among some specimens which 

 Mr. Weeks of New- York, who discovered this locality, was 

 so good as to give me, I found a beautiful rose emerald in itfs 

 matrix. It is a hexaedral prism, about one and a quarter inch 

 in diameter, the summit a plane, one of the lateral edges has 

 a truncature. About half of the diameter of the prism is free 

 from the matrix, and half an inch of the prism. The colour 

 is a pale rose, rather more transparent than the emerald. 



The colour of the mica of the Goshen granite calls to mind 

 the lepidolite or lilalite, which (formerly considered as a 

 distinct species) has now been united to mica. The lepidolite 

 of Rosena is also accompanied by the tourmaline apyre, now 

 the red tourmaline. 



Art. V. Observations on the Minerals connected with 

 the Gneiss range of Litchfield county^ hy Mr, John P, 

 Brace, of Litchfield, Conn. 



X HE gneiss formation is the most extensive of any in Litch- 

 field county, and embraces a number of very interesting mine- 

 rals. It extends east into Hartford county. On the north it 

 runs into Massachusetts, though frequently interrupted by the 

 bmestone formation, which rests upon it. It forms the prin- 

 cipal, and in many cases the only rock of the eastern and north- 

 eastern sections of the county, and of the towns of Litchfield, 

 Goshen, Warren, Cornwall, and Norfolk. In Washington and 

 Canaan, it constitutes the rock of the high mountains, and is a 

 part of the same range in the other towns, while the valleys 

 and the more moderate elevations are covered with limestone. 

 The river Housatonic appears to have made its way through 

 this range, for the same rock continues on the western side 

 of the river parallel to it in the mountains of Kent, Sharon, 

 and Salisbury. In Litchfield commences a range of porphy- 

 ritic granite, or porphyritic gneiss, which alternates with the 

 common gneiss, and in some instances rests upoh it. This rock 



28 * 



