The name is derived from the colour – the yellow of the lemon – It won’t immediately take offence at being knocked about either, since its cleavage properties are non-existent. Amethysts and smoky quartzes can also be rendered yellow by so-called burning.
This heat treatment at temperatures of between 470 and 560 degrees has to be carried out very carefully and requires a great deal of experience. However, in the course of 200 years, its application has become so much a matter of course that most of the stones available in the trade today are in fact burnt amethysts or smoky quartzes.
Only a trained specialist can recognise the signs of heat treatment at all, burnt stones having subtle stripes whilst the yellow of natural ones is cloudy.
