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There are only a few inorganic processes, in my experience at least, that will impart pinks or reds to gemstone. These involve primarily four metals - cobalt, iron, mercury and silver. We already know cobalt can induce blue, purple, amethyst, etc. and incidentally pink in gemstone. There are also two additional cobalt processes that impart pink or lavender, primarily or exclusively. Several iron compounds are red or reddish, common rust being a familiar example and at least one of these is useful in coloring gemstone. The same is true of mercury. And there are two red-silver compounds that are adaptable to coloring gemstone.... (1991) Complete Story
There are only two ways that I know of to induce black into gemstone. One of these involves carbon while the other is silver. Theoretically, there should be several other methods possible. I have tested these out however, and they have proved impractical. But black is black, so multiple means of inducing it are not needed. The two presented here are different in that one, the silver, is black with a metallic sheen or luster....
(1991) Complete Story
The use of cobalt compounds to impart blue hues to glass, glazes and enamels has been known for centuries. "Cobalt blue" glass is familiar to just about everyone. It seemed logical that cobalt compounds could be useful to impart color to gemstone and this has proven to be true. Several cobalt processes follow....
(1991) Complete Story
Various and attractive shades of blue can be induced in gemstone by the use of copper compounds. This is perfectly logical, considering that several of our blue gemstone or mineral species owe their color to the presence of copper compounds. Familiar examples of these are malachite, chrysocolla, turquoise and azurite....
(1991) Complete Story
There are several reactions well known to chemists, involving iron compounds and prussiate compounds (ferrocyanides and ferricyanides) that yield characteristic blue precipitates. All are applicable to chemical coloration of gemstone, but since they do not differ significantly for our purposes, only one is included in this book. It involves a reaction between potassium ferricyanide and ferrous sulfate, producing a blue precipitate known as "Turnbulls Blue"....
(1991) Complete Story
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