Two necklaces can both be described as gold and be built completely differently. Understanding the four terms below explains most of the price difference you see between similar-looking pieces.
Gold plated
A very thin layer of gold applied electrically over a base metal such as brass or steel. It gives the right colour at the lowest cost and is ideal for occasion and trend pieces. With daily wear the plating will eventually thin at the points that rub most.
Gold vermeil
A thicker layer of gold, usually at least 2.5 microns, applied over sterling silver rather than a base metal. Because the core is a precious metal and the coating is substantially thicker, vermeil wears much better than standard plating.
Gold filled
A thick outer shell of gold mechanically bonded to a base core, typically around five per cent of the total weight. It is far more durable than plating and can last decades with reasonable care, which makes it a sensible middle option.
Solid gold
Gold all the way through, described by carat. 9 carat is harder and more affordable; 14 and 18 carat have richer colour and higher value. Solid gold does not wear off, which is why it is the right choice for pieces you never take off.
Reading carat marks
24 carat is pure gold and too soft for most jewellery. 18 carat is 75 per cent gold, 14 carat is around 58 per cent and 9 carat is 37.5 per cent, usually stamped 375. If a listing mentions a carat number without saying solid, plated or filled, it is worth asking which it is.
