394 SYSTEMATIC DESCRIPTIOxN OF I'RECIOUS STONES 



into the surrounding blocks of trachyte, is also to be mentioned. Only in rare cases is. 

 turquoise found fillinj; up cavities in the interior of blocks of trachyte forming the breccia. 

 This mode of occurrence is of interest to mineralogists, since it shows that the formation of 

 turquoise follows on the decomposition of felspar crystals of which it often takes the external 

 form ; in other words, we have a pseudomorph of tui-quoise after felspar. 



Turquoise is found, moreover, not only in the compact trachyte and in the trachyte- 

 breccia, but also in the masses of debris formed by the weathering of these rocks and slowly 

 accumulated at the foot of the mountain. The precious stone lies loose in the detritus, and 

 is frequently coated with a white crust of weathered material, which must be removed before 

 the fine blue colour of the stone can be seen. Sometimes the whole mass of turquoise is 

 weathered to a white, crumbly material, which is, of course, useless as a gem. The 

 turquoise-bearing deposits of alluvial debris have a thickness of from £ to 20 metres : 

 close to the foot of the mountain these deposits are less thick, while at some little 

 distance away low hills have been carved out of the originally continuous mass by the 

 action of the weather. Turquoise of good qualitv is to be found only in the uppermost 

 portion of these secondary deposits to a'depth of about 2 metres ; at a depth of 6 metres 

 greenish and whitish stones of poor quality only are found, while below this turquoise is- 

 completely absent. 



There are several hundreds of mines^in this neighbourhood ; in the year 1876 there 

 were 266 being worked, but the majority ]^of them have since been abandoned. Some of 

 these mines have been worked for centuries and are mentioned in the treatise on 

 mineralogy written by the Arab Mohamed-ibn-Mansur in the year 1300. According to this, 

 work there was a legend to the effect that the richest of these mines were opened by Isaac 

 the son of Abraham, and they are consequently known as the Isaac mines. For a long 

 period they have been worked according to the best methods ; shafts to the depth 

 of 150 feet were sunk, and levels and ^galleries driven to a length of 100 feet or more, 

 though of small height and width. Pillars were left to give the necessary suppoi-t to the 

 roof, and, where necessary, ventilation ;^shafts were sunk, so that the whole working was. 

 designed and carried out in a systematic manner. 



According to the opinion of General Schindler, mining operations were probably 

 carried on up to 1725 by the Persian Government ; and it is to this authority that the adoption 

 of the methods described above was due. The management of the mines was subsequently 

 transferred to the inhabitants of Maaden, and from this time the industry began to decline. 

 Systematic methods were gradually given up ; the supporting pillars were removed in order 

 to obtain the turquoise they enclosed, all precautions were neglected, the deposits were 

 worked only with a view to rapid gain, and there was no thought for the future. Conse- 

 quently the work became very dangerous and the yield decreased ; many of the workings, 

 became inaccessible, and at some places, where formerly existed properly constructed mines,, 

 there are now funnel-shaped depressions 60 to 80 feet across and as much as 250 feet deep, 

 which have been formed by the falling in of the shafts and galleries. 



These old mines are not in all cases completely abandoned ; the excavation of 

 turquoise-bearing rock is sometimes still carried on, and both the loose rock lying in the 

 workings and the refuse-heaps outside are worked over for turquoise, usually by women and 

 children. New mines are always being sunk, and these are in almost all cases successful^ 

 since the deposit of turquoise extends throughout the whole mountainside. 



The alluvial deposit also is worked for turquoise ; the detrital material is excavated,, 

 and after the larger blocks have been sorted out the remainder is washed in order to 

 render the turquoise distinguishable. These washings at one time were of little importance. 



