The book Precious Stones a book of Reference for Jewellers was written by author Wallis Richard Cattelle Here you can read free online of Precious Stones a book of Reference for Jewellers book, rate and share your impressions in comments. If you don't know what to write, just answer the question: Why is Precious Stones a book of Reference for Jewellers a good or bad book?
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Red, sapphire-blue, and emer- ald-green are very rare and are highly valued. Orange- color, violet, canary, and rich browns also bring a good price and are growing in favor. As " off -colored" stones do not bring as much in the mar- ket as those which are colorless, many attempts to eliminate the color by the use of acids and heat have been made, but, so far as known, without success. Unprincipled dealers have also resorted to various devices for neutralizing: the natural PRECIOUS STONES 81 yel...low of off-color stones. The usual method is to paint the under side, around the culet, with violet ink or an aniline dye. This is then carefully rubbed down until the dye can- not be distinguished, but leaving enough of the coloring matter to very much improve the apparent color of the stone when faced up. The effect, of course, is only temporary, and can easily be detected by cleaning the stone with alcohol. Many of these painted stones have undoubtedly been sold by irregular dealers, who by this means induce the unwary to buy stones at what appears to be much less than mar- ket value.
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