1847.] Geology of Lewis Conntt/. 271 



and faintly glimmering lustre with a specific gravity of 4.0 and 

 its streak and powder is greenish grey. 



It is probably an impure iron ore, containing much graphite 

 and some chlorite; it is said to have yielded upon analysis 22 per 

 cent of iron. 



Its geological situation is between gneiss and Rensselaerite or 

 steatite, which here occupies a place of considerable extent in the 

 primary rocks, and appears to be of the same age with the gneiss 

 and white limestones of its vicinity. Associated with it is a rock 

 of trappean ( ?) character of a grey color, exceedingly compact 

 and tough, and containing every where disseminated through it 

 in great abundance, grains and cubic crystals of iron pyrites. 

 Near the surface, and where it has been exposed to the water, 

 the sulphuret of iron has been removed, leaving the rock spongy 

 and porous. Some specimens of this cellular rock of a light grey 

 color, resemble certain varieties of lava. Large opaque crystals 

 of quartz occur in a vein in the gneiss in the immediate vicinity. 

 Some of these crystals are aggregated in a confused manner, ex- 

 hibiting upon being broken a radiated appearance. 



The Rensselaerite of this locality exists in large quantities, 

 composing a ledge of considerable extent and is accompanied by 

 serpentine, of a dull greenish color, nearly opaque, and highly vari- 

 egated. The fractured surface of the serpentine is without lustre, 

 and although it receives a good polish, yet it wants that translu- 

 cency which gives beauty to articles made from this mineral. 

 The general color of Rensselaerite is grey, with veins of white, 

 and irregular patches of brown and black; it is easily Avrought 

 and may be procured in sufficiently large masses to be used for a 

 great variety of architectural and other ornaments. 



About half a mile from this locality to the northwest, quartz is 

 found in drussy crystals, and coating thin masses of chalcedony, 

 in seams and cavities of the gneiss, which is here composed of a 

 large proportion of this mineral. Small specimens of fortification 

 agate are common, and the chalcedony is sometimes found free 

 from its investing quartz in mammary concretions or dissemi- 

 nated in nodules through the rock. Augite associated with tre- 

 molite and a reddish brown sphene, is found near the village of 

 Natural Bridge, but not in situ. The augite is of a dark green 

 color, and the tremolite is sometimes found tinged with a beauti- 

 ful pink color. 



If to the minerals above enumerated we add graphite, in small 

 scales everywhere common, and minute quantities of magnetic 

 sulphuret of iron, we shall have completed the catalogue of min- 

 erals hitherto observed in this vicinity. 



At Indian River Lake, about two and a half miles from Louis- 

 bure, a bed of specular iron ore has been opened, and wrought to 



