-Samarskite of Mitchell County^ N. C. 201 



Art. XXVI. — Mineralogical Notes ; by Edward S. Dana. No. 

 II. — On the Samarskite of Mitchell County, North Carolina. 



Through the kindness of Mr. Joseph Willcox of Philadel- 

 phia, and of Eev. J. Grier Ralston of Norristown, I have had 

 an opportunity of examining a considerable number of more or 

 less perfectly crystallized specimens of samarskite, which be- 

 longed to their cabinets. The results are sufficiently definite to 

 give a pretty exact knowledge of the relations of the species 

 which have been till now very uncertain. 



According to information obtained from Mr. Willcox, and 

 also from Professor Bradley, the samarskite is found in the 

 mica mines situated in the mountains of Mitchell County, 

 North Carolina. The rocks of the region are gneiss and mica 

 slate, and the mines are worked in the granite veins which in- 

 tersect them. Other localities also exist, under similar circum- 

 stances, in Yancey, McDougal and Rutherford Counties. The 

 samarskite occurs in masses, generally irregular in shape but 

 ?. , .^ .feldspar, 



i coarsely crystallized, imbedded in a reddis , , 



which is very much decomposed, sometimes to a kaolin. The 

 masses vary in size, some being very large ; one obtained by Mr. 

 Willcox weighed upwards of twenty pounds. 



The immediately associated minerals are two other species of 

 the same tantalic group, described further on, and a yellow mica, 

 which may prove upon chemical examination to be of interest. 



The samarskite when pure has a deep velvet-black color, 

 though brown by transmitted light on very thin edges. The 

 luster is resinous and very brilliant, and tbe fracture distinctly 

 conchoidal. The mineral from this locality has already been 

 analyzed by Miss Ellen H. Swallow,* with the following results 

 (specific gravity 6 -756) : Metallic acids, tantalic group, 64-96, 

 SnO^ 0-16, U0 9-91, FeO l-i02, MnO O'Ol, CeO 5-17, YO 12-84, 

 MgO 0-52, insoluble residue from oxalate of cerium 1-25, igni- 

 tion 0-66 = 100-40. The metallic acids were not separated in 

 consequence of the want of material. Attention may also be 

 called here to the analysis, by Dr. Hunt, of the samarskite from 

 Rutherford County, N. C, published in this Journal, II, xiv, 

 341, 1851. ^ 



The samarskite exists in all states of purity, being sometimes 

 intimately mixed with the gangue of decomposed feldspar. 

 There are also conn, 

 decom position -produ 

 A yellow coating c 

 * Proceedinga of the Boston Society of Natural History, voL xvii, 4 

 Am. Jocr. Sci.-Third Series, Vol. XI, No. 63.-March, 1876. 



