ON THE RUBIES OE BURMA AND ASSOCIATED MINERALS. 
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form more than one-third of the mass, the remainder consisting of granules of white 
diopside, with a very fine ground mass, consisting largely of alteration products like 
scapolite and ca.lcite. 
In the other variety, the blue minerals (which vary in tint from an intense violet- 
blue to a pale lavender-blue), make up more than two-thirds of the whole, but enclose a 
number of granules of the white diopside, with some patches of decomposition 
products. 
Although these beautiful lapis-lazuli rocks have not been detected in situ , their 
presence in the ruby-gravels with rocks that have all clearly been derived from tlie 
disintegration of the gneiss of the Burma area, shows that they must occur as 
members of this gneiss series. The specimens examined and described were found 
near Thabanpin. Different varieties of the rock are shown, by determinations made 
by Mr. T. Barron, to vary in specific gravity from 2'86 to 2'9 4. 
4. Crystalline Limestones. 
As has been already pointed out, the connection of these calcareous rocks with the 
gneissic rocks among which they are intercalated, is of the most intimate character. 
With the basic pyroxene and scapolite-rocks, and especially with the pyroxenites and 
amphibolites into which these graduate, the calcareous rooks appear to be always 
closely associated. 
The idea that great beds of crystalline limestone, intercalated in a series of foliated 
rocks, must necessarily have resulted from the metamorphism of calcareous strata of 
organic origin, which have alternated with other aqueous or igneous masses, finds no 
support from the characters presented by the rocks of Burma. 
Between gneissic rocks containing numerous crystals of calcite and dolomite, and 
rocks consisting mainly of those minerals, with the various constituents of the basic 
gneisses—augites, eustatites, scapolites, phlogopites, &c.—scattered through them, we 
find every gradation, and the limestones and gneisses are also found interfoliated in 
the most intimate manner. 
That some impure crystalline limestones (hemithrenes, kalkaphanites, &c.) have 
been formed from basic igneous rocks, there is not the smallest doubt,* and in the 
same manner the study of the Burma limestones leads to the conclusion that the basic 
gneisses may undergo a corresponding metamorphosis, the breaking up of the lime- 
felspars leading to the formation of an unstable scapolite, from which and from other 
unstable minerals originate, as a consequence of further change, the calcite and 
dolomite; while the more stable silicates become enclosed in the crystallizing mass of 
carbonates, and new minerals are formed during the progress of these complicated 
chemical actions. 
The capricious manner in which the gneisses and calcareous rocks of Burma are 
* See Liebrich, ‘ Neues Jalirb. fur Min.,’ &c., for 1893, Bd. 2, p. 75. 
