GEM DISTRICTS OF CEYLON AND BUKMA—ADAMS 313 
then in progress at a point 5 miles inland, where sapphires had been 
discovered in the low-lying paddy fields. 
Practically no Europeans visited this district until the annexation 
of Upper Burma by the British in 1885. In 1889 the Secretary of 
State for India granted to Messrs. Streeter & Co., of Bond Street, 
a mining concession in the Mogok district, a seven-year lease being 
given, at a rent of 4 lakhs of rupees ($126,666) per annum, plus 16.66 
per cent of the net profits. The Burma Ruby Mines (Ltd.) was 
thereupon formed to carry on mining. In 1896 the original lease was 
renewed for a period of 14 years, and in 1910 it assumed its present 
form, and runs till May 1, 1932, there being a fixed rental of 200,000 
rupees per annum, plus 30 per cent of any excess of license income 
above 200,000 rupees per annum, the Government also claiming 30 
per cent of the net profits. The Government gave the native miners 
every protection, in so much as they were not allowed to be in any 
way disturbed in their work or dispossessed except by purchase; 
otherwise, the company holds a monopoly of the right to mine or 
wash gems over the whole area designated as the Mogok Stone Tract. 
The rubies, which form by far the most important of the gems 
yielded by this district, have their origin in the white crystalline 
limestones of the country rock, which have been described above. 
In the Mogok district (including Kathe) these limestones are in- 
tensely metamorphosed and are often very coarsely crystalline. It 
is stated that the more coarsely crystalline limestones are those which 
are richest in rubies. These gems are evidently developed in the 
limestones as one of the results of the intense metamorphism to 
which the district has been subjected. A. D. Morgan, the general 
manager of the Burma Ruby Mines (Ltd.), informed the writer that 
the sapphire, which while much less common than the ruby at Mogok, 
is nevertheless frequently found, occurs not in the limestone but in a 
rock, a specimen of which containing a large sapphire was submitted 
for examination, and which proved to be a granular white acid 
plagioclase intimately intergrown with orthoclase constituting a 
microperthite. The rubies and the other associated gems, however, 
do not occur in the limestones or their associated rocks in sufficient 
abundance to enable these to be worked for these minerals. Occa- 
sionally a native prospector will find a spot in the limestones where 
there is an unusual accumulation of rubies and will extract them, 
but this is rarely the case. The rubies and other gems are obtained 
in practically all cases from the residual or alluvial clays of the hill 
slopes or more usually of the valleys. 
In the valley workings, as at Mogok and Kathe, there is a definite 
succession in these clays, the recognition of which is very important. 
In sinking a pit or shaft this first passes through reddish or yellowish 
clay which contains no gems; beneath this is found, resting on the 
