The book Gem-Stones And Their Distinctive Characters was written by author George Frederick Herbert Smith Here you can read free online of Gem-Stones And Their Distinctive Characters book, rate and share your impressions in comments. If you don't know what to write, just answer the question: Why is Gem-Stones And Their Distinctive Characters a good or bad book?
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39), which arises from a peculiarity in the structure. Opal is mainly silica, Si0 2 , in composition, but contains in addition an amount of water varying in precious opal from 6 to 10 percent. As the original jelly cooled, it became riddled throughout with cracks, which were afterwards generally filled with opal matter, containing a different amount of water, and therefore differing slightly in refractivity from the original substance. The structure not being quite homogeneous, each crack has t...he same action upon light as a soap-film, and gives rise to precisely similar phenomena; the thinner and more uniform the cracks, the greater the splendour of the chromatic display, the particular tint depending upon the direction in which the stone is viewed. The cracks in certain opals were not filled up, and therefore contain air. Such stones appear opaque and devoid of opalescence until plunged into water; they are consequently known as hydrophane, from vScop, water, and fyalveadcu, to make appear.
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