Jewellery Metals

Platinum is a beautiful white colour and a rare precious metal. It is a noble metal which means it will never diminish in beauty and will not rust or tarnish. There are SIX metals from within the Platinum family of metals- Platinum, Palladium, Rhodium, Osmium, Iridium and Ruthenium.

There are FOUR legal standards of Platinum recognised in the UK. 800, 900, 950 and 999 parts Platinum per 1000 parts of alloy. Alloys commonly used are Palladium and Iridium (from within the Platinum family) Copper is also used as an alloy (from outside of the Platinum family).

Platinum Facts–

Specific Gravity¹ 21.43

Melting point 3223.4°F

Gold

Gold, in it’s purest form, is a beautiful yellow colour. Gold is a very easy metal to work with and is the most malleable² of all metals. It is unstable in it’s purest form for most, if not all jewellery pieces and is therefore alloyed with other metals. Alloyed gold must pass the strictest of assaying tests and must be the right colour. Adding Copper will aid the Rose Gold colour that we have seen for many years. Adding Silver and Palladium will give us the beautiful White gold colour that is so very popular. Rhodium is then used to plate the white gold.

There are SIX legal standards of fineness for gold recognised in the UK. 375, 585, 750, 916, 990 and 999 parts gold per 1000 parts of alloy.

Gold Facts–

Specific Gravity 19.32

Melting Point 1945.4°F

Silver

Silver is a lovely and relatively inexpensive precious metal. It is even more reflective than gold and an extremely easy metal to work with. It bends easily without the likely hood of cracking and the perfect metal for gifts such as trinket boxes and tankards.

Silver is affected by sulphur (found in the air) and therefore needs to be cleaned regularly. Without any intervention, Silver can become very black and cause discolouration to it’s surroundings. Ever worn a discoloured silver necklace? Unfortunately, It does not leave a very attractive mark on your neck.

Silver in it’s purest form is quite soft and needs to be alloyed with other metals to become the hardwearing, fashionable statement we all love.

There are FOUR legal standards of Silver recognised in the UK. 800, 925, 958 and 999 parts Silver per 1000 parts of alloy. Argentium Silver falls under the fineness 935 and 960 parts alloy per 1000 but have been permitted to be hallmarked as 925 Sterling or 958 Britannia.

Silver Facts–

Specific Gravity- 10.5

Rhodium

Rhodium is used to plate other metals. It is the most reflective of the Platinum family group of metals and also harder than Platinum. The most common use of Rhodium is the plating of white gold to give it it’s beautiful white colour. It can also be used on a yellow gold ring to define the “head” of the ring, showing detail. Rhodium Plating can be used on expensive pieces of silver jewellery to prevent discolouration.

Nickel in Jewellery

In the UK, jewellers have to be aware of their obligations to prevent people becoming sensitised to nickel, which can lead to allergic contact dermatitis. Sometimes alloys which could release nickel are plated with lacquer, gold or silver to prevent the nickel being released in contact with skin. In such cases, the plating must be tested with abrasives to simulate two years of wear before they are tested for nickel release. Suppliers have a duty of care to their customers and need to be able to show that they have exercised due diligence, either by carrying out their own tests under a control system or by understanding when they can rely on the tests carried out by their suppliers.

Footnotes

1. Specific gravity (SG) measures a gemstone’s density by comparing its weight to an equal volume of water, aiding in identification. ↩︎
2. Malleable= beaten into a thin sheet ↩︎