90 GENERAL CHARACTERS OF PRECIOUS STONES 



the observer. Faulty stones are sometimes set with the table towards the back, as in the 

 so-called Indian setting. Stones, on the contrary, which have no under portion are rarely, 

 and rosettes never, mounted in an open setting ; they are much more eft'ective in a closed 

 setting. A stone is held very firmly and permanently in a closed setting, and this is 

 especially the case when cement is used to fix it to the metal, as is very frequently done. 

 In an open setting, on the contrary, there is much more likelihood of the stone becomings 

 loosened from the claws which hold it, and therefore of its ultimate loss. 



Flawless stones of a good colour, which are destined to be mounted in a closed setting, 

 need only to be simply inserted in the receptacle described above. But those in which the 

 colour, lustre, or other quality leave something to be desired can be improved by certain 

 artifices in mounting and their faults more or less concealed. 



The artifice which has been longest practised is designed to conceal any dark patches 

 the stone may have, and is known as " mounting on moor." A black pigment made by mixing 

 burnt ivory and mastic is applied to those parts of the closed setting over which the lighter 

 portions of the stone will rest. The stone, when set, will then appear to be uniformly 

 coloured, the patchiness being effectively concealed. 



An artifice more frequently used is designed to improve the lustre and colour of the 

 stone to which it is applied. Thin plates of gold, silver, copper, tin, &c., which are known 

 asjbils, are laid under the stone ; they may be of their own natural colour or they may be 

 artificially coloured in some suitable manner ; in any case they show their own strong lustre. 

 Instead of metallic foils, pieces of silk with a coloured sheen or cuttings of peacock's 

 feathers and similar substances are sometimes used. An uncoloured, natural foil shows its 

 lustre and body-colour through the stone beneath which it is placed, and causes it to appear 

 more brilliant and of a finer colour than would otherwise be the case. A golden foil will 

 give a deeper yellow tint to a pale coloured stone, while a dull stone may be made to appear 

 brighter by placing beneath it a bright and shining foil. A peculiar variation of this use 

 of the foil exists in the Orient in the mounting of rubies, the back of the stone being 

 hollowed out and filled in with gold, a device which considerably heightens the effect of the 

 stone as regards brilliancy and colour. 



In the employment of foils, it is desirable that the stone and the foil should be of 

 corresponding colours. As the natural colours of the metals employed are often unsuitable 

 the foils are sometimes artificially coloured blue, red, yellow or green, these colours being 

 always placed on a white metal. Carmine, saffron, litmus, &c., are some of the pigments 

 used for this purpose, intermediate tints being obtained by mixtures ; the pigment is 

 dissolved with isinglass in water and so applied to the metal. 



Instead of using a foil, the pigment may be applied to the inside of the case in which 

 the stone is set, or even to the back of the stone itself. It is actually possible by the 

 judicious application of colour at the back of a colourless stone to give the effect of a 

 coloured stone, or even by applying a coating of various tints, to produce the effect of a 

 play of colours. This latter device is now often applied to rock-crystal or colourless glass 

 with the purpose of imitating the play of prismatic colours characteristic of the diamond. 

 Stones so treated, which have sometimes quite a pretty effect, are often used under the 

 name of " iris " for cheap jewellery, pin-heads, &c. It is especially in the Orient, however, 

 that the artifices under consideration have been developed to great perfection, Eastern 

 jewellers being possessed of marvellous dexterity, which they often make use of for the 

 deception of buyers of gems. 



By associating several stones of the same kind and of an exactly identical shade 

 of colour in one piece of jewellery a very fine effect is produced; there is however often 



