1873.] CUV Gentl.. 



cit.) of a crystal of transparent green tourmaline passing through the 

 middle of a prism of diaspore, and the whole enveloped by lamellar crys- 

 tals of pearly emerylite (damourite, Gth.). Very similar is the occur- 

 rence of slender green crystals in the pseudo-fibrous damourite. These 

 tourmalines are in all probability the result of the alteration of corun- 

 dum, or, the black tourmaline went into solution and re-crystallized in the 

 diaspore and damourite in a similar manner, as apophyllite dissolved in 

 water in a sealed tube under pressure, crystallizes out on cooling, as 

 shown by Wohler in his well known and important experiment. 



b. The association of corundum with tourmaline at the Culsagee Mine 

 deserves the greatest attention. 



There are masses of black tourmaline, which contain more or less fre- 

 quently, and irregularly disseminated through them, crystals of white 

 and yellowish-white corundum ; plates of chlorite are also, sometimes, 

 penetrating the tourmaline. The corundum crystals have particles of 

 tourmaline intermixed with them, and vice versa. On the whole, how- 

 ever, the tourmaline looks more like the matrix of the corundum. Some- 

 times there seems to be an almost imperceptible change of granular 

 corundum into tourmaline. Of the numerous specimens which I have 

 examined, two deserve a fuller description. The first is a small piece of 

 black columnar tourmaline, with a micaceous mineral, probably marga- 

 rite, and grayish-white corundum. In one case the upper part of the 

 columnar mass of tourmaline is occupied by corundum, which also pene- 

 trates into a portion of the tourmaline ; the tourmaline frequently contains 

 nuclei of corundum. The second specimen, also from the same mine, for 

 which I am indebted to the kindness of Col. C. "W. Jenks, is a pseudo- 

 morph of tourmaline after corundum. It is part of a crystal of reddish-gray 

 corundum of a little over two inches in height and about two inches in 

 thickness. It shows three planes of the hexagonal pi'ism and portions of 

 one pyramidal plane. At the upper part of this crystal, almost the entire 

 corundum has been altered into black tourmaline, leaving only a shell of 

 corundum of about one-eighth to one-quarter inch ; at its lower part the 

 corundum, although intermixed with tourmaline, is still about one inch 

 in thickness. Plates of green chlorite penetrate both the corundum and 

 the tourmaline. 



c. At the Cullakenee Mine tourmaline occurs but sparingly. It is 

 associated with foliated pink margarite and another mineral in slender 

 prismatic, longitudinally striated crystals, resembling some varieties of 

 epidote, but in too small quantity for mineralogical determination. 



d. The occurrence of tourmaline at Bell's Creek, Town's County, 

 Georgia, and Dudleyville, Tallapoosa County, Alabama, presents nothing 

 remarkable. 



12. Fibrolite. 



For a long time fibrolite has been known to accompany the corundum 

 in the Carnatic, in India, and in the neighborhood of Canton, in China ; 

 the variety much used by the Celts in the stone age has been obtained 



