Oenth,] 



370 



[Sep. 19, 



North Carolina, has already been noticed above. The spinel is generally 

 massive, coarsely to finely granular ; also met with in octahedral crystals 

 with dodecahedral planes ; the latter often indicated only by striation. 

 The crystals are often imperfect and cavernous, and mostly altered on the 

 surface, being covered with a varnish-like coating of a brownish-gray 

 mineral of vitreous lustre. The interior of the crystals like the fresh 

 fracture of the unaltered massive spinel is black. The spinel contains, 

 sometimes, grains of a reddish-brown rutile, and is always more or less 

 intermixed with grains of corundum and chlorite, the latter frequently 

 radiating from it. One specimen in the University collection is a mass of 

 chlorite, radiating from nucleus consisting of a mixture of spinel and 

 corundum. 



d. Another variety of spinel from the same locality, of which, however, 

 I found only a single specimen, resembles G.Rose's cJilorospinel from 

 Slatoust, and is found in deep leek-green or greenish-black octahedra 

 with deeply striated dodecahedral planes or in granular masses of the 

 same color ; it is associated with a pale green foliated chlorite and white 

 corundum. The spinel is often imbedded in the foliae of the chlorite and 

 not unfrequently contains particles of corundum in its centre. Its pow 

 der is pale grayish-green. 



e. The collection of Col. Jos. Willcox contains a specimen from the 

 same locality which evidently was once a corundum crystal. It measures 

 about two and a-half inches in diameter and its outlines indicate its 

 origin. It now consists of a nucleus of black spinel with a mantle of 

 chlorite. 



/. At the Cullakenee Mine spinel is of rare occurrence. I have seen 

 only one piece in which a black variety in grains and octahedral crystals 

 is disseminated through dark green foliated chlorite. 



g. At Dudleyville, Tallapoosa County, Alabama, black spinel surround- 

 ing patches of yellowish-white cleavable corundum occurs in chlorite. 



h. In connection with these observations it is worthy of notice that a 

 variety of spinel, gahnite, in association with the corundum of Gumuch- 

 Dagh in Asia Minor was discovered by J. L. Smith (loc. cit.). 



The following analyses were made : 



«l and 2, from Hindostan, by myself. 



b, from Unionville, by Dr. G. A. Koenig. 



cl, fine-grained from Culsagee, by Dr. Koenig. 



c2, coarser grained from Culsagee, by Dr. Koenig. 



d, coarse-grained and crystallized dark-green from Culsagee, by myself 



Sp. Gr. = 



ALA 



Fe,0 3 



Cr,O s 



FeO 



MnO 



MgO 



Si0 2 



Corundum 



100.87 100.49 100.68 100.71 99.96 100.41 



100.49 



