878 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



The expression is still in use even now, especially in the case of exceptionally fine stones, 

 although it has long been known with certainty that the supposed oriental opal localities in 

 Egypt, Arabia, Cyprus, Ceylon, &c., do not in fact exist. As early, indeed, as the end of 

 the seventeenth century Tavernier, the French traveller and dealer in precious stones, stated 

 his belief that precious opal was to be found only in Hungary, but this statement appears 

 to have been overlooked. 



The Hungarian opal mines are situated fifteen miles to the south-east of Eperies. At 

 the foot of Simonka, the highest mountain of a wild, forest region, is the small settlement 

 of Dubnik, which owes its existence to the occurrence of opal in that region. Here are 

 found the many beautiful Hungarian stones so much prized as gems all the world over. 

 There is little doubt but that the Romans obtained their opals from this identical spot, 

 while records of the working of the deposit in the fourteenth century are actually in 

 existence. 



The mother-rock of the opal is here a brownish or greyish volcanic rock, technically 

 described as a mica-hornblende-andesite. The portions of the mother-rock which contain 

 opal are much weathered and bleached, the felspar being altered to kaolin and in part to 

 •opal. .The precious opal occurs in nests in certain bands of the andesite, which are 

 separated off from the barren rock by sharp lines of division or by open crevices. In these 

 nests precious opal is accompanied by hyalite, milk-opal, and other varieties of common 

 opal, into which it gradually passes. The precious opal occurs in much smaller proportion 

 than the common opal, so that from a large mass of material after the removal of the 

 common opal, only a small amount of opal of gem-quality will be left. Here, as elsewhere, 

 the opal frequently occurs in rounded masses, indicating that it has been deposited from 

 solution. The water, by the agency of which the opal was foi-med, was probably supplied 

 by hot springs; although now dry in the immediate neighbourhood where the opals are 

 lound, such hot springs are met with at no great distance away. Moreover, it is said that 

 specimens of opal, showing no play of colour, are found saturated with moisture underground 

 in the mines, and that on exposui-e to the air they dry and the play of colours gradually 

 appears. 



In former times the mining of opal was carried on entirely by private enterprise. The 

 -deposits of this locality were worked principally by the inhabitants of the village of Czerwenitza, 

 which is situated about an hour's journey to the south. They obtained the gem out of 

 surface workings, traces of which remain at the present day in the form of heaps of debris. 

 A certain proportion of stones have been set free by the weathering of the andesitic rock, 

 and such are said to have been brought to the surface from time to time in the operation 

 of ploughing or by the agency of rain-storms. The exclusive right of mining opal in this 

 region was first claimed by the Government in 1788, and in place of surface workings, the 

 method exclusively adopted till then, systematic underground mining operations were 

 commenced, but in a very short time were entirely abandoned. For several decades after 

 this all work ceased, when the present system of leasing the mines to private individuals 

 began to be adopted. It was reported in 1877 by Professor Gerhard vom Rath that the 

 rent per annum was 15,000 florins, while the working expenses for the same period 

 amounted to 60,000 florins, so that to leave a margin of profit the yield could not have 

 been very small. By improved methods of mining it was still further increased, so that the 

 mines became very lucrative. 



At the present time the workings are confined to the Libanka mountain, situated 

 about half a mile west of Dubnik. On the east side of the mountain, opal mines and old 

 debris-heaps extend for four and a half miles from north to south. The galleries, which 



