Diamonds And Luxury

Different minerals differ very considerably in their conductivity for heat, and this character may serve in some cases to distinguish minerals similar in appearance from each other. The majority of precious stones are good conductors of heat, and on this account they are cold to the touch, since the heat of the hand is quickly conducted away. Glass is a somewhat poorer conductor and hence a glass imitation is not so cold to the touch as a genuine stone, since the warmth of the hand is not so quickly conducted away. The difference in the power of conducting heat of genuine stones and their imitations may thus, under certain conditions, afford a means of distinguishing between them ; the specimens tested must not, however, have remained long in the hand nor have been otherwise warmed, neither must they be too small. It is said to be possible for an expert to select, by the sense of touch alone, a diamond out of a bag containing a large number of pieces of glass of similar size and shape.

Amber can be used on earrings also round diamond earrings. Amber is one of the feeblest conductors of heat; its conductivity is much less than that of glass, hence a piece of amber can be easily distinguished from its imitation in yellow glass, since it feels so much warmer to the touch. Another substance having a feeble conductivity for heat is jet, a variety of coal, which is frequently made use of for mourning ornaments. An opaque, black glass is often used for the same purpose, but a single touch of the finger tips is all that is needed to enable an expert to distinguish between the two.

Check this minerals. A device for distinguishing a genuine from an imitation stone, depending upon the power of conducting heat, is to breathe upon the stone. The moisture of the breath will condense upon the genuine stone with more difficulty than upon glass, and when condensed will disappear again much more rapidly, since the precious stone is both more rapidly warmed and more rapidly cooled than is glass.
For the purpose of distinguishing rough stones, their fusibility before the blowpipe may sometimes be made use of. All glass imitations are easily fusible before the blowpipe, while few of the minerals used as precious stones can be so fused. Red garnet is one such mineral, and can be easily distinguished from other red stones which are infusible before the blowpipe, such as ruby and spinel. The application of this test is naturally limited to rough stones, splinters of which can usually be detached for examination.