ON THE RUBIES OF BURMA AND ASSOCIATED MINERALS. 
219 
pseudomorphs of corundum occur. Among the minerals found replacing corundum 
as pseudomorphs are muscovite (damourite), various forms of spinel, andalusite, 
fibrolite, cyanite, margarite, chloritoid, zoisite, ripidolite, and other chlorites, various 
vermiculites, kaolin, and other substances. The hydrates of alumina, diaspore and 
gibbsite, are seldom, if ever, found as pseudomorphs after corundum because (as is so 
well seen in the case of the diaspore of Dilln, near Schemnitz) the hydrated oxides 
of aluminium very readily enter into combination with silica, forming various silicates. 
The spinels, so commonly associated with corundum, are also frequently altered ; 
pseudomorphs after spinel in hydrotalcite, serpentine, talc, and hydrous biotites being 
well known to mineralogists. 
Between the years 1849 and 1851, the late Professor J. Lawrence Smith, 
published several important memoirs on corundum and emery.'" One very striking 
fact established by the experiments and analyses of this able observer, was that all 
forms of corundum and emery (excluding the fine gem-varieties known as ruby, 
sapphire, &c.) contain water up to about 3 per cent., with varying proportions of 
silica, lime and iron oxide. Lawrence Smith also showed that the abrasive power 
of corundum steadily diminishes as the proportion of wmter present in it increases ; 
and he was clearly of the opinion that the water in these specimens of corundum is 
combined with a portion of the alumina forming a hydrate disseminated through the 
mass. In connection with this subject he remarks : “Of all the specimens that I 
have collected, none offer so much interest as those composed of diaspore embedded 
in corundum ; here we see the two minerals passing one into the other, without being 
able, in many places, to distinguish the line of separation, so imperceptible is the 
gradation. After what has been said in respect to corundum, it is not astonishing 
to see the connection of alumina, more or less hydrated, with a hydrate of alumina of 
definite composition/’t 
To another distinguished American mineralogist, the late Dr. F. A. Genth, we are 
also indebted for many valuable observations which illustrate the ease with which 
corundum becomes hydrated, and then, by combination with silica, is converted 
into a great variety of crystallized minerals. In his valuable memoir on “ Corundum, 
its Alterations and Associated Minerals,” published in 1873, Dr. Genth showed by a 
series of careful analyses, how remarkable have been the series of metamorphoses 
which this mineral has undergone, in the great corundiferous belt of the Eastern 
United States.]: Bammelsberg, it is true, in the second edition of bis ‘ Handbuch 
der Mineralchemie,’ published in 1873, threw some doubts on the results announced 
by Genth ; § but in a later memoir, published in 1882, the latter author fully established 
* ‘Am. Journ. Sci.,’ series 2, vol. 7, (1849), p. 283. Hid., vol. 9 (1850), pp. 289, 354. Ibid., vol. 11 
(1851), P . 53. 
t Ibid., p. 58. 
t ‘ Proc. Am. Phil. Soc.,’ vol. 13 (1873), pp. 361-406. 
§ 1 Handbuch der Mineralchemie,’ 2nd edition, Spec. Theil, p. 147. 
2 F 2 
