TETRAHEDRITE, TENNANTITE, AND NACRITE. 183 



I could not obtain in sufficient quantity for examination ; from 



an imperfect examination I conclude that it is muscovite. The 



other mineral — a soft, unctuous, talc-like mineral — is nacrite, 



composed as follows : 



Silica 65.02 



Alumina 26.11 



Oxide of iron 2.20 



Manganese trace 



Potash and soda 1.18 



Water 4.98 



99.49 

 These minerals came from an exceedingly interesting 

 mine in Arkansas that is as yet almost unexplored. I have 

 obtained a description of it from Professor Cox, and I think 

 it would be well to give it here; for, besides being likely to 

 prove of considerable commercial value when properly ex- 

 plored, there will doubtless be found many interesting mineral 

 species there. 



The Kellogg mines are situated ten miles north of the city 

 of Little Eock, in Pulaski County, Ark. The country in the 

 vicinity is rolling; the highest hills are about two hundred and 

 seventy feet above the water-level of the neighboring streams. 

 The surface rocks are thick, and thin beds of sandstone alter- 

 nating with shales occupying the base of the coal measures. 

 The rocks are but little disturbed, and are for the most part 

 horizontal. There are no metamorphic rocks showing them- 

 selves at the surface nearer than Little Rock, on the south side 

 of the Arkansas River. Innumerable veins of milky quartz 

 are seen traversing the sandstones and shales. 



About seventeen years ago lead- ore was discovered at these 

 mines by Mr. Kellogg ; companies were organized and mining 

 operations carried on extensively for about one year, when the 

 nattering accounts of the gold discoveries in California caused 

 the miners to leave, and the work, which had been badly con- 

 ducted, was abandoned. Many tons of the ore, which is an 

 argentiferous galena (containing sixty to two hundred ounces 

 of silver to the ton), were extracted from the mine, and finally 

 the greater part was shipped to England and sold at a good 

 price. A smelting furnace has been erected on the grounds, 

 but for lack of skill the proprietor never succeeded in working 

 the ore profitably ; consequently the impression was produced 



