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34
PRECIOUS STONES.

trained eye and touch. And with a spectroscope, a polariscope, in addition to a good hand magnifier or pocket lens, such an array of evidence may be marshalled that there can remain but few cases in which the identity of a stone shall continue doubtful. But for the purpose of the artistic employment or appreciation of precious stones such a table as that given on pages 5 and 6 will prove more useful than any recondite method of inquiry. Some of the uses of that tabular arrangement of conspicuous optical qualities may be gathered from the following examples. Referring to the shape of stones we note that their boundaries are either plane or curved. Now if we have to use, in any piece of personal ornament, stones having curved surfaces, it will not answer in general to associate with them other curved surfaces, like those of the en cabochon moonstone; and especially is this the case where the size of the stone, as well as the character of the curved surface, is nearly identical; but a happier result will be attained by combining a step-cut stone with one having a curved surface. Again, citing an example from the series of adjectives expressing qualities of surface, it will be found that gems having an adamantine lustre assort better with those which present the less brilliant surface known as waxy, than they do with those which show a nearer approach to the adamantine surface, and which are called resinous. The diamond and the jargoon do not improve or bring out each other's qualities, for they have too many points in common; but the diamond accords well with the pearl, and the jargoon with the turquoise, that is, the adamantine with the pearly, and the resinous with the waxy. Looking, now, into the substance of stones, rather than on their surface, their relations to the transmission of colourless light furnish many illustrations of wise and unwise, or effective and defective combinations. For example, chatoyant stones, like cat's-eyes, do not associate well with translucent stones, like the chrysoprase and the chalcedony—the translucency of the latter confuses, because it resembles too closely, the chatoyancy