1373.] *>"" [Gcrith. 



Although the object of many of these analyses was only to determine 

 the species, the material for investigation was selected with great care. 

 Some of them, notwithstanding, contained minute quantities of corun- 

 dum, by which the per centage of the silica or alumina is slightly in- 

 creased ; the majority, however, fully agree with the established compo- 

 sition of damourite, the constituents of which have the oxygen ratio : 

 RO : R,0 3 : Si0 2 : H 2 = 1 : 9 : 12 : 2. 



Only the damourite from Crowder's Mountain would give for water 

 the ratio : 3. This is the result of three determinations, all agreeing 

 with each other. Some of the damourite varieties have a portion of the 

 alumina replaced by the ferric oxide. 



17. Ephesite. Lesleyite. 



In his investigations on emery, J. L. Smith (I. c.) describes under the 

 name " e})7iesite," a mineral which he states to have a lamellar structure 

 and to resemble white cyanite. I will give below the analysis of ephesite, 

 by Dr. Smith, and also one, which I made from material kindly furnished 

 me by him for my investigations on corundum. It will be seen that they 

 compare pretty well. I must add, however, that Dr. Smith's analysis 

 should be considered the better, because he had a larger quantity and 

 probably cleaner material for his examination. The main object of rny 

 analysis was to see whether ephesite contains a mechanical admixture of 

 corundum, which was most conclusively proven. 



Not having had an opportunity to see ephesite, Dr. Isaac Lea called 

 (I. c.) a similar mineral from Unionville, lesleyite. He recognized the 

 change of the hard corundum into soft minerals and in the absence of 

 analyses, he considered all those which were fibrous and compact as iden- 

 tical. This is undoubtedly a very excusable error, because it is next to 

 impossible to distinguish these minerals without chemical tests, and 

 credit should be given to him for having brought to light these interest- 

 ing varieties. 



Of the fibrous and compact damourites I have already spoken, the 

 margarite belonging here, I shall consider afterwards ; I now will dwell 

 only upon such varieties, as have been generally recognized as trui 

 lesleyites. Some of these have been the subject of investigations by S. P. 

 Sharpless,* and Dr. J. L. Smith,! and of observations by G. J. Brush.}; 

 There are three principal varieties of lesleyite. 



a. The first is fibrous and divergent. It is slightly grayish- white, the 

 surface is discolored by ferric hydrate, but interior of the mass appears 

 to be free from it. Its lustre is pearly inclining to silky, it is scratched by 

 fluorite, but scratches quartz easily, and is associated with scaly damour- 

 ite. 



b. The second variety resembles the first very much, but is more ferru- 



*S. P. Sharpless, Sill. Journ. [2] XLVII, 319. 



tJ. L. Smith, Sill. Journ. [2] XLVIII, 254. 



$G. J. Brush, Appendix to 5th edit, of Dana's Mineralogy, New York, 1872. 



