Discriminating between diamond and CZ

After a tip from Orchid, I placed a 2.5mm CZ and a 2.5mm diamond face-down on a sheet of white paper which had had fine alternating-colour lines drawn along it. On careful inspection with a loupe, it was apparent that one couldn’t see the coloured lines through the diamond, but they were fairly visible, though distorted, seen through the CZ (see picture in the right side-bar). The implication, in addition to giving a test for discriminating between the two materials, is that light passes from the back to the front, then gets reflected from the lined paper, before passing again to the back and out to the eye. One wonders what difference there might be if both stones were laid face-down on a light box. I also tried adding a fine-silver backing to a CZ, mindful of the beauty of Swarovski crystal. The result was very disappointing; the translucent quality of the CZ was replaced by a sense of rather dirty grey in some of the darker areas, though the general amount of light reflected didn't seem affected. I'm pretty sure there's a good reason why no-one sells foil-backed CZ...

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