Citrine

Citrine is the yellow-to-orange variety of quartz, coloured by traces of iron. Natural citrine is genuinely uncommon; most stones sold as citrine are heat-treated amethyst or smoky quartz, which turn yellow or reddish-orange when heated, and the deep reddish tone marketed as Madeira citrine is almost always heated material. This is worth knowing because much of the folklore printed for citrine is really borrowed, the natural stone having been too rare historically to accumulate a tradition of its own. In modern crystal practice citrine is the merchant's stone or success stone, associated with wealth, the solar plexus centre and the sun; these associations date from the twentieth century and rest on the yellow colour. Citrine is one of the accepted November birthstones alongside topaz. It should not be confused with the yellow of true topaz, a different and harder mineral.

Because natural citrine is rare, the stone has long travelled under other names in the trade: heat-treated quartz of this colour has been sold historically as Spanish topaz and Madeira topaz, borrowing the more prestigious mineral's reputation, and Kunz records the same confusion running the other way, with genuine yellow quartz sometimes passed off as topaz to buyers unable to tell the two apart. In Scotland a related smoky-to-yellow quartz found in the Cairngorm mountains, called cairngorm, was cut for centuries into the pommels of dirks and sgian-dubhs and the brooches of Highland dress, a distinct regional lapidary tradition built on the same mineral species as citrine.

Citrine is yellow to orange quartz, and the single most important fact about the commercial stone is that most of it did not start out that way.

Natural citrine, coloured by traces of iron in the quartz structure, is genuinely uncommon and is usually a pale, slightly smoky yellow. Amethyst, coloured by iron in a different oxidation state produced by natural irradiation, is abundant. Heating amethyst to somewhere in the region of 400 to 500 degrees Celsius converts the colour centres and turns the stone yellow, orange or reddish brown, permanently and irreversibly. The process is cheap, it is carried out on an industrial scale on Brazilian and Uruguayan amethyst, and the resulting material fills the world's citrine counters.

Some indicators distinguish it. Heated amethyst often shows a strong orange to reddish cast and colour zoning inherited from the original crystal, and the trade name Madeira citrine generally denotes it. Natural citrine tends to be paler and more evenly coloured. Neither test is conclusive without laboratory work, and disclosure practice in the trade is inconsistent.

The confusion runs deeper than treatment. Citrine and yellow topaz were not distinguished in the older trade at all, and citrine was sold as topaz for centuries. That is why November carries both stones in the modern birthstone lists, and why any pre-twentieth-century reference to a yellow topaz has to be treated as an unresolved identification.

None of the traditional attributions attached to citrine can be assumed to describe the stone now sold under the name.