Precious Metal Alloys

When buying a piece of jewellery containing a Yellow diamond, one of the choices you need to make is which precious metal you want the jewellery to be made from. The choice you make will have a direct effect on the price of the jewellery item you are after.

One of the most common metals used in jewellery is gold. As pure gold is very brittle, it is not suitable for use in jewellery as it is not rigid enough. To get around this problem manufacturers mix gold with other metals to make a stronger metal alloy which is more suitable for use in jewellery. Often cheaper metals such as silver and copper are used as alloys with gold.

The purity of gold content is measured in carats. Pure gold has a carat rating of 24 carats. A ring made from 18 carat gold is 18 parts gold out of every 24 parts of metal used. In the same way a ring made from 9 carat gold is 9 parts gold out of every 24 parts of metal used. The more gold which is used the higher the carat value will be and in turn the more expensive the piece of jewellery will be.

The current method in use for measuring gold content is the metric measurement which is a value out of 1000. For example 9 carat gold is 9 parts gold out of every 24 parts total which equates to 37.5% gold content or 375 parts gold out of every 1000 parts total.

To help make individuals aware of what they are buying, nearly all jewellery containing precious metal content is hallmarked at a regional government assay office. This is simply a stamp on the jewellery to confirm what the percentage of precious metal content is.

There are only 4 assay offices in the UK. These are London, Birmingham, Sheffield and Edinburgh. Each assay office has its own stamp so that you can tell which office hallmarked the jewellery. These are shown below.

The hallmarks relating to the precious metal content are as follows:

Current UK Hallmarks Used By Assay Offices


The main types of gold alloys used in jewellery are as follows:

Alloy Carat Percentage
  • 9 Carat Gold
9 37.5% or 375
  • 14 Carat Gold
14 58.5% or 585
  • 18 Carat Gold
18 75% or 750
  • 22 Carat Gold
22 91.6% or 916
  • 950 Platinum
  95% or 950

As a rule, we tend only to use 750 gold or 950 Platinum for our high quality diamond jewellery.

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