164 
MR, C. BARRINGTON BROWN AND PROFESSOR J. W. JUDD 
2. Alluvium . 
In the larger valleys of the district there are extensive deposits of alluvial matter, 
consisting of clay, gravel, and sand, which have been laid down by the streams 
flowing through them. The materials of these vary in different portions of the same 
valley, being in the upper part of Mogok composed of a brown sandy loam resting 
upon coarse gravel, beneath which is an admixture of clayey materials containing 
gravel and sand, together with many rounded blocks of gneiss. In the lowest 
portion of the gravel and sand, rubies and quantities of garnets are found. This 
rests upon an under-clay which, in places, is a white floury kaolin containing white 
mica, the result of the decomposition of the bed rock. The thickness of the whole is 
from 10 to 12 feet. 
Lower down the valley, in front of Mogok, the thickness of the top clay is from 
15 to 22 feet, and the ruby-bearing sand and gravel beneath varies from 5 to 7 feet. 
Beneath this comes a stiff yellowish under-clay containing a few water-worn pebbles. 
The ruby-bearing material is composed of yellowish sand, in which are coarse pebbles, 
and rounded blocks of gneiss. It is difficult to say of what the remainder of 
the deposit is composed after the under-clay is reached, for the miners cannot be 
induced to dig deeper than the base of the ruby-bearing sand, the under-clay being- 
soft and dangerous to sink through, its weight breaking their light timbering. 
Near Taungwee the alluvium is composed of yellow and red loamy clay having a 
thickness of 24 feet, beneath which is from 3 to 4 feet of yellowish sand with large 
water-worn blocks of gneiss and pegmatite, resting upon an under-clay of a micaceous 
character, derived from the decomposition of pegmatite. 
Between Taungnee and Mintada, away from the river, the alluvium is of a red 
and yellow loam amongst large blocks of pegmatite, at the base of which is a thin 
irregular layer of ruby-bearing gravel. The whole has a thickness of 15 feet, and 
rests upon the white decomposed bed-rock. Nearer Mintada the deposit is all of 
blackish clay and sand. 
In the Yeboo valley, near the village of that name, it is formed of a brown loam 
passing into gray clay, of 12 feet in thickness, with dark grey ruby-bearing sand and 
gravel. I was unable to find any sections of the alluvium of the Kathay and 
Kyatpyen valleys, owing to there being no twinlones at work in that district; and 
the numerous remains of small round pits, long since abandoned, did not show the 
nature of the deposit passed through. 
In the Injauk valley near Bernardmyo are old alluvial workings in the form of pits, 
some of which are 12 feet in depth, sunk through clay of bluish-grey and yellowish 
colours, with much slightly water-worn quartz gravel which came from the gem-bear¬ 
ing layer at the bottom. The greater portion of the excavated material has been 
washed away by rain. Some very perfect specimens of rock crystal are seen scattered 
over the surface of the ground. These mines, it is said, produced sapphires of good 
quality in former years. 
