QUARTZ (AGATE): ENGRAVING 521 



although they are not esteemed as highly at the present day, yet the number of stones 

 treated in this way is not inconsiderable. 



The varieties best suited for engi-aving upon, but not devoted exclusively to this 

 purpose, are the onxyes, including onyx pi'oper, chalcedony-onyx, carnelian-onyx, and sard- 

 onyx. These can be so cut as to display a white or light figure against a darker-coloured 

 background. The flatter an onyx is, and the more regular are its layers (Plate XX., 

 Figs. 5a, b), the better suited it is for this purpose ; hence Brazilian agates with their 

 plane layers (Plate XIX., Fig. /;) are specially suited for onyx stones, and on that account 



Fig. 91. Agate-grinding workshop of Herr August Wintermantel, at Waldkirch (Baden). 



more valuable. Stones which are to be engraved have the form of plates, and are cut out 

 of even-layered agates, so that the plane of the plate is parallel to the banding of the 

 stone and is of one uniform colour. The uppermost layer is then partly cut away, so that 

 the portion allowed to remain has the outlines of some figure, usually a portrait. It is 

 generally arranged that the figure cut out of the uppermost layer shall be white or light 

 coloured, this being well thrown up by the background afforded by the coloured lower 

 layer. A cameo cut in carnclian-onyx is represented in Plate XX., Fig. 7, and others in 

 Figs. 93 and 94. Sometimes the uppermost black layer is cut through and the figure 

 worked in the underlying white layer, as in the intaglio of Fig. 92 ; in this case also one 

 gets a white figure on a dark background. A seal-stone of camelian with a letter engraved 

 upon it is represented in Plate XX., Fig. 6. A kind of stone much sought after for 

 cameos is one in which a white layer is partly covered by a red layer. It is then possible 

 to pi'oduce a figure showing two colours, the red layer being utilised to represent hair, 

 clothing, or such like. The work is performed, as we have already seen, by a tool known 



