Precious Metal, Nickel & Hallmarking

Advice section hero Precious Metals

Here you will find a wealth of information about precious metals, regulation and hallmarking.


Often referred to as a hard metal, this can be misleading. Pure platinum is softer than pure gold and it is the other constituents of the alloy that make it hard wearing. The most common 950 (95% pure) alloy is the hardest of the precious metals used in jewellery. What mustn't be forgotten is that even so, it is far softer than other common metals like steel and chrome. Platinum is very durable and takes a fine polish that is resistant to wear. It is naturally a greyish white and is often rhodium plated to make it even whiter. It requires a higher level of craftsmanship and also being rarer than gold, explains why it is worth more.

Platinum is often referred to as a hard metal, which can be misleading. Pure platinum is softer than pure gold, however when mixed with the appropriate alloy, platinum is the hardest of the precious metals used in jewellery. It is far softer than other common metals like steel and chrome.

Platinum Facts

Pure platinum only has a hardness of 40HV, which is very low and generally considered unsuitable for jewellery. To make it harder platinum is alloyed with other metals, most commonly ruthenium, iridium, palladium and gold or base metals such as copper or cobalt. As with other metals, platinum can also be hardened by further processing such as burnishing and hammering - this type of work will harden the piece making it more resistant to wear and deformation. In general, platinum with a hardness below 100HV is not recommended for casting unless further processing work is carried out.

The facts about the alloys Platinum -5% Palladium (Pd) has an annealed hardness of 60HV, which is very low and is only suitable for the certain castings and delicate settings. It is too soft for ring shanks and is easily dented and scratched.

  • Pt-5% Iridium (Ir) has an annealed hardness of 80HV, which means that it is too soft for rings. However, it has high work hardenability and in the cold worked state is 140HV. This makes it suitable for catches and springs.
  • Pt-5% Ruthenium (Ru) has an annealed hardness of 120HV and is a general-purpose alloy with good machinability. However, there is some doubt about its suitability for castings.
  • Pt-5% Gold (Au). This is a good alloy but the annealed hardness is 90HV and is not suitable for rings.
  • Pt-5% Cobalt (Co) has an annealed hardness of 135HV and is a good casting alloy. It has a faint bluish tinge and is slightly magnetic.
  • Pt-5% Copper (Cu) has an annealed hardness of 120HV and is generally regarded as a good all-purpose, medium - hard alloy.

As expected some alloys are more suitable for casting then fabrication and machining, and vice versa. Pt-5% Cobalt (Co) was created especially as a casting alloy and with a hardness of 135 HV is relatively resistant to scratching. It takes twice as long for Pt-5% Cobalt (Co) and Pt-10% Iridium to exhibit the same loss of surface reflectivity as Pt-5% Iridium. It is recommended that jewellery made from Pt-5% Iridium should only be sold if further processing work has been carried out. This includes decorative engravings and other finishes other than high polished, as well as further processing such as burnishing and hammering.

Remember while choosing a harder alloy and undertaking further processing work on platinum items can reduce the amount of scratching and lengthen the time it takes for signs of scratching to appear. Sooner or later all platinum jewellery will exhibit wear-induced dulling, as will jewellery made of any other metal. So it is important to remind your customer to take special care of their jewellery. Advise them not to wear it when doing jobs around the house, gardening, DIY etc, and let them know that jewellery can also be damaged by shopping trolleys, dog leads, prams, door handles, handbrakes, even washing-up. Some of the information for this fact-file was obtained from The Goldsmiths Company; it may vary slightly and should only be taken as guidance.


Another precious metal which is being increasingly used by UK jewellery companies is palladium. Palladium, a platinum group metal, is normally used at a fineness of 950, or 95% pure. It is strong and durable, but has approximately half the density of platinum and weighs around a third less than gold. Being light means it lends itself well to the creation of larger, more dramatic designer items that are currently fashionable, especially earrings, cufflinks, necklace, bracelets and bangles where weight is important. Palladium is a very bright almost blue ‘white’ and unlike 18ct white gold alloys does not need to be rhodium plated. It wears in much the same way as platinum does and can be highly polished or presented in a matt finish.


Yellow Gold

Many believe, including some jewellers, that the higher the carat of gold the softer the metal (gold is a soft metal). Therefore 9 carat gold, being alloyed with other metals tends to be more resistant to scratching than say 22 carat gold. This is not necessarily the case. Many manufacturers producing 18 carat gold jewellery ensure that, as the jewellery is higher quality, the alloy is harder wearing. This way when you have bought a piece of fine jewellery it will last a long time.

White gold and rhodium plating

Pure gold is yellow in colour but to satisfy the demand for white precious metals ‘white’ gold alloys can be produced by alloying yellow gold with naturally white precious metals such as palladium or silver, or non-precious ‘white’ metals to reduce the yellowness of the resulting alloy. Gold bullion suppliers now sell a range of graded white gold alloys which can be compared against a published scale of “whiteness”. However, white gold is routinely electroplated with Rhodium, a precious white metal which imparts a bright white finish. Depending on the level of wear, this finish wears off and white gold thus requires more care and maintenance to keep it bright.

If the underlying white gold is a yellower grade then it will start to show through as the rhodium wears. Consumers should bear in mind that their white gold jewellery may require re-plating at variable intervals depending on the amount of wear and the thickness of rhodium plating which can be applied to the jewellery. Some designs, particularly those with sharp edges and corners, may only be suitable for a thin plating of rhodium.

Red and other colours of gold

Red or rose gold is created by increasing the amount of copper in the alloy. Introducing other metals (or removing them completely) can make other colours of gold, including unusual tones such as green and blue but these are not generally available.

Durability of gold

Many people believe that due to its higher purity and the inherent relative softness of the pure metal, that 18ct gold is less durable than 9ct alloys. In fact, with modern alloy technology, there is little to support this belief. Today’s 18ct alloys are equally as durable as their 9ct equivalents and offer the additional benefits of tarnish and corrosion resistance, to say nothing of appealing to the consumer’s desire for a more pure and natural product.


Silver, one of the precious metals, can achieve a great polish and does not tarnish in its pure ­­­form. Most silver jewellery is silver combined with other metals as an alloy. This makes it more suitable for general use. Sterling silver, like some other precious metal alloys, can oxidise over time. Properly maintained silver jewellery improves with age and develops a beautiful patina. Treat your silver well, care for it properly and it will reward you with a long life and a special look.


Your watch is a very intricate piece of engineering and works non-stop day after day. You would not expect your car to do this without a service so follow the instructions on servicing. As a guide a service every three or four years should help it last for decades.

Give your watch a quick check on a regular basis, making sure that the strap or bracelet is securely attached to the case. If you have a mechanical watch wind it in a clockwise direction. Often it is recommended that you do this about the same time each day. Remove the watch from your wrist when winding so as not to place undue pressure on the winder. Water resistance is often misunderstood, for example, a watch saying 30 metres on the dial sounds like it is perfectly safe to swim in. The 30 metres is actually a static pressure that the watch can take. Did you know that just jumping into a pool can exceed this pressure therefore possibly letting water into the watch?

If you really have to know the time when you are in the pool, it is recommended that you have a watch with a 100-metre water resistance or greater. Even then don't wear it in the bath or while taking a shower.

Mixed metals

Until very recently jewellery made using a combination of different precious metals, or of precious metals mixed with non-precious metals could not carry a hallmark on the precious metal element. The law has now been changed and consumers should look out for innovative designs incorporating a variety of materials such as gold mixed with stainless steel, titanium or bronze.

Nickel in jewellery

In the UK, jewellers have to be aware of their obligations under the Dangerous Substances and Preparations (Nickel) (Safety) Regulations 2005 which is designed to prevent people becoming sensitised to nickel, which can lead to allergic contact dermatitis.

Because trace elements of nickel can be found in many precious jewellery alloys and particularly in costume jewellery, jewellers have to be confident that when they are designed to be worn in direct and prolonged contact with the skin, eg a ring, necklace, bracelet, watch back or parts of earrings (but not a brooch) any nickel which is released from an item of jewellery is within permitted levels. For piercing post assemblies, this release level is a maximum of .2 micrograms per square cm per week. For other products (ie not piercings) it is a maximum of .5 micrograms per square cm per week. The tests are carried out under controlled conditions in a commercial testing laboratory or in certain assay offices.

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.

NAJ does not recommend the use of terms such as “nickel free”, “hypoallergenic” or “nickel safe” because items which release small amounts of nickel can comply with the regulations but could be in contravention of the Trades Descriptions Act. Retailers who use such terms may have a poor understanding of the regulations and their obligations.

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.


Cultured pearls are formed inside oysters. As they are of organic origin, although they are beautiful, they are particularly susceptible to damage. For this reason, you should treat cultured pearls with great care. Cosmetics including perfume and hairspray should be applied before you put on any cultured pearl jewellery, otherwise the nacre or skin can become permanently damaged. After wearing, clean them with a soft dry cloth. Should you need to wash your cultured pearl jewellery, do it with water and maybe a drop or two of detergent. Obviously don't get cultured pearl stud earrings wet as it may affect the pearl cement.

Don't use any form of chemicals, as they are most likely to damage the cultured pearls. Cultured pearls are soft and any rough treatment such as carrying in a handbag or putting them loose in a jewellery box may also damage them. Wrap them in acid-free tissue for protection. Everyday wear and the natural constituents of your skin can have a detrimental effect on the silk used to thread your cultured pearls. Get a National Association of Jewellers member to check them regularly. The frequency of rethreading depends on many different factors, but once a year is a good idea.

Natural, enhanced, manmade, synthetic, created etc

It is all very confusing for those not 'in the know'. Natural is relatively simple, this would be a gemstone that is entirely in its natural state other than being cut and polished. Enhanced is a term used for natural gems that have been improved synthetically in a permanent way. This has been going on for over 100 years and is an accepted practice that doesn't require mentioning to the public in most cases. An example of this would be the colour improvement in zircons in Victorian times.

There are however some enhancements that do require description. An example would be the lasering of diamonds to remove inclusions (nature's fingerprints). Travellers buying diamonds while on holiday in America, for example, are often sold these without any declaration (a very good reason to buy instead from a National Association of Goldsmiths member back home).

Manmade and synthetic gems are simple to define, though there are many terms used to try and detract from the fact that these are grown in a laboratory. Created or Kimberley are terms that are commonly met. Valuation for Insurance When you leave your jewellery for appraisal your jeweller will need to know the purpose for which you require the finished valuation. Items of jewellery are valued differently for different purposes. You might wonder about the gap between the insurance value of an item and the amount you would get, as a private individual, if you chose to sell the pieces.


Metal Hardness

Hardness is determined by pushing a pointed object into the surface of the metal and then measuring the indentation. As a rule, the deeper the impression, the softer the metal; the harder the metal, the more scratch resistant it is. Resistance to scratching that is determined by metal hardness is measured in Vickers (HV).

The Worshipful Company of Goldsmiths and the start of regulation

The Worshipful Company of Goldsmiths, more commonly known as the Goldsmiths' Company, is one of the Twelve Great Livery Companies of the City of London and received its first royal charter in 1327.

The Livery Companies have their origins as trade guilds of the Middle Ages. The word "gild" is Anglo Saxon for payment because early members paid a subscription. Livery first meant an allowance of food and clothing, then a distinctive uniform or badge to distinguish one company from another. The word "worshipful" refers to the practice of the early guilds to gather together for Christian worship. Founded to regulate the craft or trade of the goldsmith, the Goldsmiths' Company has been responsible since 1300 for hallmarking gold and silver articles.

Today the Company continues to carry out this statutory function by operating the London Assay Office and also promotes excellence in the design and craftsmanship of silver and jewellery as part of a wider role in support of its craft and industry. In mediaeval times, craftsmen of the same trade gathered together to form voluntary associations, with the aim of mutual worship, support, care and protection, in a world where deprivation and death were all too prevalent. From these early associations evolved more formal organisations known as guilds, with rules and regulations for membership and standards of craftsmanship. Throughout the cities of Western Europe, the guilds took on a practical, social and economic dimension as they grew. In the City of London, they found expression in the City Livery Companies. The most important began life in the 14th century and secured their authority for regulation through royal charters. With the periodic ratification of its charters, the Goldsmiths' Company has survived plague, famine, fire and war, sustaining throughout the centuries its prime concern: the maintenance of the standards of precious metals epitomised by the practice of hallmarking.


The purity or fineness of gold is measured by assaying. Traditionally this means weighing the gold alloy and then using a cupellation furnace to remove the alloying metals and any impurities, allowing the final pure gold residue to be weighed and compared with the weight of the original alloy and the fineness can then be calculated. Increasingly, new technology is replacing cupellation but this remains the reference test. Nowadays, minimum fineness is expressed in parts per thousand, so 9 ct is 375, 14 ct is 583 (rounded to 585), 18 ct is 750 and 22 ct is 916.


Hallmarking in the United Kingdom has a long history dating back 700 years. It is the independent testing and marking of gold, silver and platinum wares by an Assay Office and guarantees conformity to all legal standards of purity. As such it represents the oldest form of consumer protection in the United Kingdom.

The word "hallmark" originally meant "marked at Goldsmiths' Hall" when the Goldsmiths' Company was the sole authority entrusted with this statutory requirement. A hallmark indicates Who, What, Where, When:

Who made the article - the sponsor's mark What the precious metal content is - the fineness mark Where it was hallmarked - the Assay Office mark When it was hallmarked - a unique letter mark for each year Authority for hallmarking comes from the Hallmarking Act 1973. Articles of precious metal may not be described as being gold, silver or platinum unless they are hallmarked or specifically exempt. In 1999 the Act was amended to reflect developments in the European Union. As a result, the fineness symbol and date letter are now voluntary marks. Still based in Goldsmiths' Hall and using the most up-to-date technology, the London Assay Office, now one of four assay offices in the United Kingdom, hallmarks several million articles every year. It also provides the Secretariat of the Association of European Assay Offices.

Assay Office contact details

London Assay Office
Goldsmiths' Hall, Gutter Lane, London EC2V 8AQ
020 7606 8975

Birmingham Assay Office
1 Moreton Street, Birmingham B1 3AX
0121 236 6951

Dublin Assay Office
Dublin Castle, Dublin 2
003531 475 1286

Edinburgh Assay Office
Goldsmiths' Hall, 24 Broughton Street
0131 556 1144

Sheffield Assay Office
Guardians' Hall, Beulah Road, Hillsborough, Sheffield S6 2AN
+44 (0)114 231 2121

The British Hallmarking Council
St. Philip's House, St. Philip's Place, Birmingham B3 2PP
0121 200 3300