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Ch. 9: Heat tests on Gems

Ch. 9: Heat tests on Gems Page of 118 Ch. 9: Heat tests on Gems Text size:minus plus Restore normal size   Mail page  Print this page
54                         PRECIOUS STONES
character, and even to become singly or doubly refract­ing, opaque or transparent, to heat-rays, according to the nature of the impurity or to some slight change in the crystalline structure, and so on.
In some of the specimens the gypsum showed a heat-penetration index of 0.90, and amber of 0.056, but mostly not within the third point. In all cases the heat-penetration and refraction were, shown by electric re­corders. These figures are the average of those obtained from tests made in some cases on several stones of the same kind, and also on isolated specimens. Not only
Ch. 9: Heat tests on Gems Page of 118 Ch. 9: Heat tests on Gems
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