208 
MR. C. BARRINGTON BROWN AND PROFESSOR .T. W. .TFDD 
The results obtained by separating the silicates from the carbonates by the action 
of dilute hydrochloric acid in the case of the beautiful blue limestone from the ruby 
cave of Burma, were as follows :—The proportion of insoluble residue was found to 
vary in different cases from 2 per cent, to 3‘34 per cent. The amount of insoluble 
minerals in a number of average fragments, weighing together 688 ’46 grammes, was 
21 ”23 grammes. This gives a percentage of 3d7, which is probably near a true 
average. The limestone of the Burma ruby cave is a pure calcite, almost wholly 
free from dolomite. 
5. Gravels and Earthy Deposits. 
These deposits are made up entirely of' fragments of the rocks found in situ. 
The fragments are sometimes all angular or sub-angular ; but well-rounded water- 
worn pebbles are by no means unfrequent in them. The fine materials of the earths 
consist of scales of kaolinite, mica, &c., stained to a yellowish-brown tint by 
ochreaceous material. J. W. J. 
VII. Mineralogy. 
In studying the series of minerals obtained from the interesting corundiferous 
localities of Burma, there are three classes of facts which appear to have a special 
significance and to be worthy of study for their important scientific bearings. 
First. The association of the various species of minerals in the rocks of Burma, 
which contain the rubies and other gems ; and the comparison of this association 
with the facts observed in other areas, where the same gems occur. This study 
of paragenesis constitutes a line of enquiry of great promise to the mineralogist. 
Secondly. This association of minerals in particular rocks of different areas is 
suggestive of the conditions under which the Burma gems—the corundum (ruby), 
spinel and tourmaline (rubellite)—may have been formed, and the chemical reactions 
to which they owe their origin. 
Thirdly. Not less interesting than the question of the origin of the ruby and 
its associated gems, are the problems concerning their alteration and destruction, 
which, as we shall show, have been continually going on, as the result of both 
deep-seated and surface action. 
1. Association of Minerals in the Gem-localities of Burma. 
The investigations of Mi-. C. Barrington Brown have shown that the parent 
rock of the famous rubies of Burma (the “ pigeon’s-blood rubies”) is undoubtedly 
a highly crystalline limestone which encloses crystals of corundum, spinel, pyrrhotite, 
graphite, phogopite, and many other minerals. Equally decisive is the evidence 
that he has brought forward to show that the fine red tourmalines (rubellites) of the 
same district in Burma do not occur in these limestones in association with the 
