130 



Miner aJugiad Journeij. 



Besides this form, the following twin-crystal was frequently noticed. 



M on T, or M' on T'. Reflec. G. 11 5° 36' 



T on T' .... " " 129 35 



a on a' .... " " 109 24 



a' on a' " " 138 32 



M 



In size, they vary from half, to one and a half inches in length, by 

 one eighth, to one inch, in diameter. Their planes are very symetri- 

 cally extended, free from striae, and in general possessed of a high 

 degree of lustre. Their color is yellowish green, often quite dark ; 

 and the smaller crystals are semi-transparent. In turning them round 

 very near my eye upon the axis of the Reflective Goniometer, I no- 

 ticed in them, a dichroism, hitherto unobserved, so far as my knowl- 

 edge extends, in this species. Whenever the edge formed by the 

 meeting of the planes M and T came opposite my eye, the Ught which 

 flowed through the crystal was of fine emerald green color ; whereas 

 opposite the other edges, it was of a yellowish brown. 



The Magnetic Iron Ore, in veins from eight inches to several 

 feet in width, and obeying the stratification of the rock, occupies 

 the south western summit of the mountain, traversing the gneiss, 

 whose strata are here nearly vertical. The surface being quite 

 steepf no difficulty has been encountered from water in following the 

 ore. One vein has been pursued up the mountain for a distance 



