ON THE RUBIES OF BURMA AND ASSOCIATED MINERALS. 
161 
red, pink, and white patches of soil exposed by landslips, is very pleasing. The 
numerous tivinlone mines (see p. 184) in operation on the flat with their tall yellow 
bamboo balance poles, form a striking feature and give an air of activity to the scene. 
C. B. B. 
IY. Geological Structure of the District (see Map, p. 183.) 
1. Hill Wash. 
As a result of the action of rain and atmosphere, continued through an immense 
period of time, portions of the rocks of the country, composed mainly of gneiss, have 
been completely decomposed to greater or lesser depths, and the interbedded crystal¬ 
line limestone dissolved to a considerable extent, setting free the insoluble constituents. 
The resulting materials have been washed down the mountain sides, where they now 
form thick, flanking masses of loamy clays of various colours, from dark red through 
light red to pinkish, brown, yellow, and white, together with the harder constituents 
of the disintegrated rocks. During this process a rude sorting of their component 
parts has been effected, the sands and gravels being collected together and deposited 
in irregular layers near the base of the clays. The minerals these rocks contained 
have thus been liberated and deposited amongst the sands and gravels, where old 
mountain streams have placed them, amongst huge hard water-worn blocks of rock 
which have been detached from their original positions and rolled down. Owing to 
the sorting process, the ruby-bearing earthy clays and sands are found in leads at 
various levels up the beds of steep gullies and in the red clay hill spurs bordering 
them. They are iriva.riably in irregular sloping patches, one overlapping the other. 
Where the sands and gravels are mixed with a dark brownish earthy clay, resulting 
from the disintegration of the crystalline limestone, they are richer in gems such as 
the ruby and spinel; and these are more frequently found on the eroded surface of 
the limestone beds themselves. 
This superficial deposit covers large portions of the mountainous tract described ; 
but it is only in certain localities where it is worked for the gems it contains. Owing 
to the mines in this deposit being large open cuttings, called by the natives Hmyaud- 
wins, they afford fair sections disclosing its nature. In order to show this more 
clearly, a few of these sections will now be described. 
The face of the cutting of No. 11 mine, some 20 feet in depth, is composed of 
reddish loamy clay, completely covering the pinnacled and eroded surface of layers of 
crystalline limestone. In the lowest portion of this, amongst the large cavities, is a 
brown earthy clay, mixed with very slightly watenvorn pebbles and sand, which 
contains minerals, including rubies. Embedded in the deposit amongst rounded gneiss 
boulders is one block of hornblendic gneiss. This section is an interesting one, as 
showing how completely the limestone outcrop is hidden from view by the hill wash 
covering. 
MDCCCXCVI.—A. Y 
