86 GENERAL CHARACTERS OF PRECIOUS STONES 



than that of faceting. It is mentioned by writers of the earliest historical times, and 

 specimens of this art dating back to very early times are preserved in our museums. The 

 art of engraving precious stones is still piactised, especially in Italy, but the popularity, at 

 the present day, of engraved gems is not comparable with that of faceted stones. The 

 cutting of precious stones with a view to the production of an engraving is known as the 

 glyptic art, and is thus distinguished from the grinding of facets upon the stone, which can 

 scarcely rank as an art. 



Engraved precious stones are generally known as gems. The device engraved upon a 

 gem is either sunk in the stone so as to lie below its surface, in which case the gem is known 

 as an intaglio ; or the device is in relief so as to lie above the surface of the stone, a gem so 

 engraved being known as a cameo. Intaglios are frequently used for seals or signets to 

 produce a raised cameo-like impression ; for this purpose they are commonly engraved with 

 a crest or monogram. Cameos, on the other hand, have no application of this kind, but are 

 used merely as ornaments. The art of engraving intaglios is known as sculpture, while that 

 of producing cameos is known as tornuture. Of the two arts, the former is the more 

 ancient, but the antiquity of the latter is well established by the number of cameos, in the 

 shape of a beetle — the so-called scarabs — found in Egyptian tombs. 



All kinds of stones, whether hard or soft, opaque or transparent, have been and ai'e 

 employed in the production of intaglios. The harder the stone the sharper and clearer 

 will be the engraved figure, and the more irksome and lengthy the process of engraving. 

 The engraving of the diamond, in spite of its hardness and the consequent difficulty in 

 working, is occasionally effected ; ruby and sapphire have also been sometimes worked in 

 this manner ; the harder precious stones are, however, much less frequently engraved than 

 those which are softer and offer less resistance to the process. Specimens of this art, dating 

 from the earhest times, are still in existence ; these comprise engravings executed on emerald, 

 aquamarine, topaz, chrysolite, turquoise, rock-crystal, amethyst, plasma, chalcedony, 

 carnelian, agate, heliotrope, opal, lapis-lazuli, nephrite, obsidian, magnetite, and many other 

 stones. At the present day the materials most frequently used are quartz and chalcedony, 

 together with such varieties of these as agate, onyx, &c., also haematite and a few others. 

 The material of the intaglio shown in Plate XX., Fig. 6, is carnelian , another example of 

 intaglio is shown in Fig. 92. 



Transparent stones cut as cameos are very rarely seen ; opaque stones of fine colour 

 are usually chosen for the purpose, those constituted of differently coloured bands, as in 

 onyx and sardonyx, being specially suitable. Different portions of the device of a cameo 

 cut in such stones may lie at different levels ; thus, supposing for example that the device 

 is a human figure, a white layer may be worked to form the face and hands of the figure 

 and a black layer for the hair and garments. In the cameo shown in Plate XX., Fig. 7, the 

 white figure and the red background are at different levels in the red and white-banded 

 stone ; other specimens of this kind of work are represented in Figs. 93 and 94. Opaque 

 stones of one colour throughout, such as turquoise and malachite, are also used in the cutting 

 of cameos ; the material of the Egyptian scarabs is very frequently not a precious stone at 

 all, but serpentine or some similar stone. In Italy, where the industry of cameo-cutting 

 especially flourishes, the shells of certain marine molluscs are employed instead of the stones 

 mentioned above ; in these shells, as in many agates, red and white layers occur in regular 

 alternation. The majority of cameos sold, for example, in Naples, are made of such material ; 

 they may be readily distinguished, however, from a genuine cameo, cut from onyx, &c., by the 

 fact that a shell-cameo is soft enough to be scratched with a knife, and will effervesce when 

 touched with a drop of acid. 



