LAPIS-LAZULI : OCCURRENCE IN ASIA 



44S 



Fig. 83. Occurrence of lapis-Iazuli in the neigh- 

 bourhood of Lake Baikal. (Scale, 1 : 2,450,000.) 



occasionally one which shows a bright red centre surrounded by a dull, dark blue border. 

 The latter case would suggest that dark blue lapis-lazuli is derived by the weathering of red 

 or violet material, and if this be so, the dark 

 blue stone of Badakshan must be regarded as 

 having undergone more alteration than has the 

 violet and red material of Lake Baikal. 



The output of these mines is very uncertain, 

 and the working of the deposit is never a very 

 profitable undertaking. Moreover, in new ground 

 there is nothing to indicate the presence or 

 absence of the mineral, and the choice of a 

 favourable spot for fresh excavations is entirely 

 fortuitous. 



In the narrow valley of the small stream 

 Talaya, which has a length of thirty versts 

 (twenty miles) and flows into Lake Baikal two 

 versts to the south of Kultuk, there are on 

 the left side steep clifl's of white doloraitic lime- 

 stone which in places are overlain by granitic 

 rocks. In the limestone are veins filled with a 

 marly limestone containing scales of mica, blocks of compact limestone, and nodules and 

 fragments of lapis-lazuli (Fig. 84). Up to the year 1853 three mines were being worked 

 in this deposit. The material obtained was poor in quality, however, and after the 

 discovery of the richer deposits on the Malaya Bistraya the mines were abandoned. 



The mines on the Sludianka stream are situated twelve versts south of the village of 

 Kultuk ; they were worked for a very long period, were abandoned for a time on account of 

 the poor quality of the lapis-lazuli and 

 the hardness of the rock in which 'it 

 was enclosed, but later were reopened. 

 Here also the mineral is found embedded 

 in white marble at the junction of that 

 rock with granite and gneiss, the latter 

 of which is frequently associated here 

 with marble. Pebbles of lapis-lazuli are 

 also found in the bed of the stream 

 throughout its entire course of thirty- 

 five vei'sts. The material found in this region has a great range both of colour and 

 quality ; the best is of the deepest and most beautiful ultramarine-blue ; the least valuable 

 is pale and cloudy ; while the medium qualities sometimes show beautiful transition tints 

 between blue and violet or celadon-green. 



The richest deposits are those discovered in 1854 on the Malaya Bistraya {i.e. Little 

 Bistraya) stream. All the best stones from this region have come from this particular spot, 

 and the material found there as a whole is wonderfully uniform in quality. The mines are 

 situated on the left bank of the stream, ten versts above its mouth, and no others in the 

 neighbourhood have been worked for a long period. In this region granitic rocks 

 predominate, and in the mountain ridge, which forms the right side of the valley, there 

 are almost vertical beds of white, granular, dolomitic limestone, which has been altered by 

 the granite on which it rests ; the lapis-lazuli occurs in the loose material which fills up the 



Fig. 84. Occurrence of lapis-lazuli on the Talaya Kiver, 

 Lake Baikal, (a, Granite ; J, Veins in limestone ; e, Nodules 

 of lapis-lazuli.) 



