264 A Book of Precious Stones
	that the article which he purchases contains a sap­phire, emerald, or diamond, representing so much intrinsic value, without considering whether the best use of it, from an artistic point of view, has been made; or whether for the same outlay much more pleasing effects might not have been obtained from other stones. In the grouping of gems, with regard to effects of colour, lustre, tex­ture, etc. certain combinations often seen are far from ideal, while others rarely seen would be ad­mirable. Thus a combination of the diamond and turquoise is not a proper one, since the opacity of the latter stone deadens the lustre of the former. The cat's-eye and diamond make a better combina­tion, and so do the more familiar diamond and pearl. Colourless stones, such as the diamond or topaz, associate well with deep-coloured ones, such as amethyst and tourmaline, each serving to give light and tone to the other. Diamond and opal as a rule detract from each other when in combina­tion, since each depends upon " fire" for its attractiveness. While there are variations innumerable of design and device in mounting gems, there are practically but two basic methods, the mount d jour (two French words, meaning to the light) and the encased mount. The ordinary manner of setting gems in rings, the stone held by a circlet of claws, permitting a view of it, or through it, from all points, illustrates the