1882.] ^<5J [Genth. 



c. The Presley Mine in Haywood county, N. C, has furnished some 

 very remarkable specimens of corundum, altered into feldspar as well as 

 mica (muscovite). 



a. The corijndum at that Mine is generally of a grayish-blue color, 

 sometimes in large crystals, more or less altered into the two minerals 

 mentioned. Frequently in the interior of the crystals, when the altering 

 agents had access by fissures or otherwise, small patches of white, cleav- 

 able feldspar may be seen, often, but not always, surrounded by mica. 

 In other specimens, very little of the original mineral is left, and the gray- 

 ish blue, deeply striated nucleus of corundum is surrounded by an aureole 

 of exceedingly delicate, subfibrous mica (damourite) variable in thickness 

 from 1 to over 20°"" in diameter. "When in immediate contact with the 

 corundum the altered mineral is generally almost compact and scarcely 

 presents a crystalline structure, farther away from it, it becomes more 

 scaly, the scales increasing in quantity and size ; often large plates are 

 mixed with very fine scales of mica. The color of the compact and sub- 

 fibrous mica is generally of a very delicate pink, but sometimes also white 

 with silky lustre ; the scales are mostly white witli a yellowish or silver- 

 gray tint. Masses of such, partly altered corundum, of over ISO™"" in 

 diameter have been found, containing nuclei of nearly unaltered corun- 

 dum of from 10 to 100°"" in diameter, sometimes showing the beginning 

 of a change into mica and albite, where the alteration has been facilitated 

 by fissures. 



/?. A very remarkable specimen from the same mine is an imperfect 

 crystal of muscovite with plates of 35"'"* in diameter, showing three or 

 four sides of a six-sided prism. The upper and lower part of the original 

 crysral are broken off, but it is still over 50"™ in height. It has an 

 eminently basal cleavage, easily splits into thin elastic laminae and has 

 a brownish-gray color. In the center of the crystal and also in the 

 lower part are remnants of smooth, bluish-gray cleavable corundum 

 from 8 to 10™™ in diameter. On the exterior portion of the muscovite 

 are small quantities of albite. 



y. The alteration of corundum into muscovite and albite is perhaps 

 still better represented by a specimen, consisting of an imperfect crystal 

 of muscovite of a brownish-gray color, of over 80™™ in diameter and a 

 thickness of 40™™, to which is attached, especially on one side, white, 

 cleavable albite. The whole specimen is over 150™™ long, about 85™™ 

 broad and 45™™ thick. Disseminated through the mass, both the mica 

 and the feldspar, are remnants of crystals of grayish-blue corundum. 

 Generally there is a thin seam of mica between the corundum and feld- 

 spar, but, in many places, the latter is in immediate contact with the 

 corundum. The corundum shows distinctly the action of dissolving 

 agents, it is rounded, smooth, as, if waterworn, sometimes corrugated, etc. 



The whole mass has the appearance of a coarse granite, in which the 

 quartz is replaced by corundum. 



