298 SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



stones exceeding 8 or 10 carats in weight are rare. As we have already seen, spinels are far 

 more free from faults than are rubies, so that it is not surprising to find that spinels of fine 

 quality are much more abundant than rubies of the same description. 



The value of a spinel varies with its colour and transparency, but is always less than 

 that of the ruby. A perfectly transparent "ruby-spinel," up to and not exceeding 4 

 carats in weight, is worth, at the most, about half as much as a ruby of equal weight ; thus 

 a 1-carat " ruby-spinel " will fetch from £5 to £7 10s. The value of larger stones is 

 considerably greater. " Balas-rubies " and other varieties of spinel of the best quality are 

 about half the value of " ruby-spinels " ; when exhibiting the milky sheen, described above, 

 they are worth still less. 



Although small specimens of precious spinel are much more abundant than large stones, 

 yet a certain number of the latter are in existence. A " ruby-spinel " of 56^f carats, valued 

 at 50,000 francs (^2000), is mentioned in the inventory of the French crown jewels drawn 

 up in 1791 ; also a " balas-ruby '' of 20^^ carats, vahied at 10,000 francs, and two smaller 

 stones of 12j^ and 12 carats, valued respectively at 3000 and 800 francs. Another famous 

 spinel of large size, the " Black Prince's Ruby," is set in the English crown ; it is often, 

 though erroneously, referred to as a true ruby. Probably the two largest spinels known are 

 those which were shown at the Exhibition of 1862 in London ; both were flawless stones of 

 perfe:t colour and were cut en cabnchon. The one weighed 197 carats, and on re-cutting 

 gave a gem of 81 carats ; the other weighed \0%\ carats before and 72|^ carats after 

 re-cutting. 



With respect to mode of occurrence spinel is closely related to corundum, since it is 

 found under the same conditions and chiefly at the same localities as are ruby, sapphire, and 

 the other varieties of corundum. Like corundum, spinel is essentially a mineral of the 

 primitive rocks, being found in gneisses and schists, and especially in crystalline limestones 

 interfoliated with gneisses ; it also occurs in limestones formed as the result of contact- 

 metamorphism. The most important localities for spinel are briefly mentioned below, the 

 reader being referred for descriptive details to the account of these same localities given 

 under ruby and sapphire. 



In Upper Burma the different varieties of precious spinel ai-e, in association with the 

 Tuby, of common occurrence both in the white crystalline limestone or marble and in the 

 gem-sands derived from this. Three-fourths also of the precious stones which are brought 

 for sale by the natives from the neighbouring Shan States are spinels. 



Next in importance to Burma coiue the gem-gravels of Ceylon, especially of 

 the interior of the island in the neighbourhood of Kandy. Fine crystals are not 

 •common, but a beautiful, transparent blue spinel, which will be referred to again below, 

 is peculiar to the locality. Here also the mother-rock of the spinel is a granular 

 limestone. 



Spinels are abundant in the ruby mines of Badakshan. As early as the thirteenth 

 century, spinels, together probably with rubies, were collected by the famous Venetian 

 traveller, Marco Polo, in the province of Balascia on the Upper Oxus. This province is 

 identical with the Badakshan of the present day, and the term " balas-ruby " is said to be 

 derived from the place-name Balascia. Spinels are found in association with the rubies, 

 which are sold in Tashkent, and which are said to come from the Tian-Shan Mountains ; 

 also with those found at Jagdalak in Afghanistan, and with the rubies and sapphires of 

 Siam. 



Spinels occur in the gem-gravels of Australia, usually as rounded grains. Here again 

 they are specially abundant in the New England district and the Cudgegong and Macquarie 



