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jewelry glossary

Antique jewelry glossary

Welcome to our extensive antique jewelry glossary with around 1,500 jewelry related entries.If you feel you are missing an explanation, feel free to let us know and we will add it.

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Heat treatment

The process of changing or eliminating the colour of a natural gemstone or a synthetic gemstone by the application of controlled heat, due to a rearrangement of the atoms of the tinctorial agent.

Examples are:

  • an amethyst which, when heated, becomes yellow (and resembles citrine) or green, and when more highly heated becomes colourless
  • a yellow topaz which changes to rose-pink
  • a zircon of reddish-brown colour which changes to blue or yellow or becomes colourless
  • a dark quartz (morion) which becomes brown and then colourless
  • an aquamarine or beryl of greenish-yellow colour which changes to blue

The changes are not in all cases permanent. The process of changing the colour of a metal by heating. Examples are: gold which changes to reddish when the presence of the copper in a low-carat alloy sometimes results in a varicoloured effect; copper which changes as a layer of cuprous oxide forms, going through yellow, bronze, light blue, and dark blue.

From: An Illustrated Dictionary of Jewelry, autor: Harold Newman, publishers: Thames and Hudson

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