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ME. C. BARRINGTON BROWN AND PROFESSOR J. W. JUDD 
associated, and the unexpected manner in which the one type of rock seems to 
replace the other, has been illustrated by Mr. Barrington Brown in his account of 
their relations as seen in the field. 
In their general appearance and texture these metamorphic limestones of Burma 
exhibit the widest diversity. Sometimes, as in the bands that occur at Bernardmyo, 
they are finely granular (saccharoid) in character ; at other times,ms is well exemplified 
in the ruby-cave at Mogok, the individual crystals of calcite may grow to the size of 
a man’s fist. There are few more beautiful limestones than this rock of Mogok, with 
its delicate blue tint and the large and brilliant cleavage-faces of its twinned calcite 
crystals. 
The crystalline limestones of Burma also differ greatly from one another in the 
proportions and the nature of the minerals enclosed in them. Some of the limestones 
are almost free from foreign minerals, while others are made up to the extent of more 
than half their mass of various silicates, oxides, and sulphides. 
Many of the limestones contain a notable proportion of dolomite. Sometimes the 
dolomite grains are of the same size as those of calcite, with which they are inter- 
grown, and only differ from them by the comparative rarity of twius following the 
—- -§R (HO) planes of the crystal and their insensibility to the action of cold dilute 
acids. In other cases, however, the dolomite in these limestones make up aggregates 
of minute rhombs, which are left behind when the rock is digested with acetic acid 
or with dilute hydrochloric acid in the cold, but are rapidly dissolved in boiling acid. 
We may group these crystalline limestones into two classes according to the nature 
of the foreign minerals that are present in them, as follows :— 
(1 ) Cipollinos , in which the predominant foreign constituent is a micaceous 
mineral, and the rock usually exhibits a more or less distinctly foliated structure, 
thus passing into a calc-schist (kalkschiefer). Rocks of this class occur at Mandalay 
Hill and on the Mogok side of the pass on the Bernardmyo road, near Toungnee 
mountain, and many other localities too numerous to specify. Similar limestones are 
very common as fragments in the various pits opened in the alluvial deposits for 
obtaining rubies. 
(2.) Calciphyres .—This old name of Brongniart's may be conveniently applied to 
the rocks, consisting of a ground mass of calcite crystals, through which various 
pyroxenes and other minerals are distributed like porphyritic constituents. The 
well-known red limestone of Ballyphetrich (Tiree marble) was made by Brongniart 
the type of his Calciphyres, and there are many interesting points of resemblance 
between the Hebridean limestone and the very beautiful rocks of the same class in 
Burma. 
The minerals that have been found, in these Burma limestones are very numerous. 
They may be conveniently divided into two classes as follows :— 
(«.) Minerals which are identical with those found in the associated basic gneisses, 
pyroxenites, and amphibolites. 
