214 
MR. C. BARRINGTON BROWN AND PROFESSOR J. W. JUDD 
several other minerals which have been brought from Burma, but have not yet been 
detected in the limestones. Among these are beryl (aquamarine) and danburite. 
The absence of certain minerals from the Burma limestone is verv noteworthy, 
especially if we compare the association of minerals there with that found in other 
corundiferous limestones—like those of Orange County, N.Y., and Sussex County, 
N.J., and the well-known rock of St. Gothard. So far as my observations go, 
I can find no trace of the silicates with fluorine and boric acid. Neither topaz, 
the tourmalines, the axinites, or the chondrodites have been found, though most of 
these minerals are found abundantly in the corundiferous limestones of the Eastern 
United States and the Alps. Chondrodite has been reported as occurring in Burma 
limestones ; but, I think, the yellow decomposition products of corundum may in some 
instances have been mistaken for the mineral in question. 
[Since this was written, my friend, Mr. T. H. Holland, F.G.S., of the Geological 
Survey of India, has sent me some remarkable specimens of a limestone from Sagyin, 
in which very fine spinels are found associated with much chondrodite. My friend, 
Dr. W. T. Blanforp, informs me that a limestone of this kind also occurs just 
outside Mandalay. But of the occurrence of chondrodite in the Mogok limestones, I 
have hitherto been unable to obtain any evidence.—October 7th, 1895.] 
2. Origin of the Corundum, Spinels, and other Minerals occurring in the Limestone 
of Burma . 
The investigations carried on with respect to the mode of origin of the Burmese 
gems, which have been detailed in the preceding pages, show that the parent rock of 
the corundum and spinel is a limestone—either highly crystalline or saccharoidal— 
which contains a great variety of included minerals, silicates, and oxides, with 
graphite and pyrrhotite. The limestone which the rock of Burma most closely 
resembles is undoubtedly that of Orange County, N.Y., and Sussex County, N.J., 
which are associated with the remarkable deposits of zinc ore at Franklin Furnace 
and Ogdensburg, N.J. In comparing the minerals found in these limestones of 
North America, as given by Mr. J. F. Kemp, # and those of Burma, we shall be struck 
by the large number of species in common. But there is one striking and significant 
difference that must be borne in mind. The tourmalines and chondrodites so 
abundant in and characteristic of the North American limestone, appear to be nearly, 
if not altogether, absent from the Mogok limestone. 
At St. Gothard, corundum is also found embedded in a dolomitic limestone, and 
here, too, it is associated with tourmaline. 
The researches of Lawrence Smith! and Tschermak], have shown that the emery 
# J. F. Kemp, “ The Ore Deposits at Franklin Furnace and Ogdensburg, N.J.” (‘ Trans. N.Y. Aead. 
Sci.,’ vol. 13 (1893), pp. 76-98). 
t ‘Am. J. Sc.,’ vol. 7 (1849), p. 283; ibid., vol. 10 (1S50), p. 354; and vol. 10 (1851), p. 53. 
t ‘ Min. u. Pet. Mitth.,’ Bd. 14 (1894), p. 311. 
