Gold 

Gold is a dense metallic element (Au) mined from the earth. It is relatively inert and extremely malleable. Deposits of gold form in minute seams in rock strata. Where gold bearing rocks have been eroded, gold is sometimes found in the sand and gravel of river beds, where because of its density, it sinks to the bottom and can be separated by simple panning in running water. Where the gold is found in rock strata it has to be extracted by blasting and crushing the rock and using chemicals such as cyanide to dissolve the gold.  Dealing with the potential environmental impacts of the residues of these processes requires careful environmental management. Sometimes gold is extracted as a byproduct of mining other metals such as copper.

Gold has been sought after for centuries and has many uses including as a universally acceptable store of value and therefore an international currency. It has also been valued for centuries as a material for making jewellery.  However gold jewellery is not fashioned from pure gold – which would be far too malleable to be a practical proposition.  The ‘gold’ of which jewellery is created is fashioned from a range of gold alloys and is a mix of metals containing pure gold as well as silver and base metals such as copper and zinc.   The resulting alloys allow different physical properties and colours to be achieved.  More information about gold can be found at the World Gold Council website at www.gold.org.

The composition of gold alloys used for jewellery production varies around the world but in the UK there are four, strictly enforced standards with regard to the amount of pure gold they include. These are 9ct, 14ct, 18ct and 22ct.   Pure gold has 24 parts (carats) in 24 of gold, therefore 9 ct gold has 9 parts of gold and 15 parts alloying metals and 18 ct gold has 18 parts of gold and 6 parts of alloying metals. 

Assaying  

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 

Undercarating is the practice of selling gold, platinum or silver alloys which contain less precious metal than is inferred in their description. In the UK it is an offence to describe in the course of a trade or business a description indicating that something is wholly or partly made of gold, silver or platinum, or  to supply an article to which such a description has been applied, unless it carries an approved hallmark indicating that it has been sampled and tested by one of the four UK assay offices in London, Birmingham, Sheffield or Edinburgh.  Marks applied under the Hallmarking Act 1973 show the mark of the sponsor or supplier, the minimum fineness (which also indicates the precious metal eg 750 for 18 ct gold, 925 for sterling silver, or 950 for platinum) and the mark of one of the four UK Assay Offices which carried out the sampling and testing and where the sponsor is registered.  Small or delicate items (less than .5 gm for platinum,  1 gm for gold and 7.78 gm for silver) are exempt from hallmarking.  There is an international convention which governs the mutual recognition of hallmarks.

More details on this and on all aspects of precious metal hallmarking can be found on website of the British Hallmarking Council. www.britishhallmarkingcouncil.gov.uk

22ct gold  In order to bear a 22ct gold (916) hallmark a piece of jewellery must be made of an alloy containing a minimum pure gold content of 916 parts per 1000. Only a very small percentage of jewellery sold in the UK is made of this alloy.  Because it is very close to pure 24 ct gold, these alloys are popular in Asian countries where gold jewellery is purchased or given as a store of wealth.

18ct gold  In order to bear an 18ct gold (750) hallmark a piece of jewellery must be made of an alloy which contains a minimum pure gold content of 750 parts per 1000.  Most 18ct gold will contain 75% gold, 16% silver and 9% copper a combination which allows it to be easily formed into jewellery, whilst ensuring its durability. This alloy is the choice for discerning customers seeking high quality, luxury jewellery designs.

14ct gold  In order to bear a 14ct gold (585) hallmark a piece of jewellery must be made of an alloy containing a minimum pure gold content of 585 parts per 1000. This standard is much used in the USA but is not so common in Britain.

9ct gold  9ct gold alloys must contain a minimum fine gold content of 375 parts per 1000 which means that the major part of a 9ct gold alloy comprises base rather than precious metal. 9ct gold is widely used in the UK for the production of less expensive jewellery designs but it is very popular and durable.

White gold and Rhodium Plating

Pure gold is, of course yellow in colour but to satisfy 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 can, and does, wear 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

Silver, like its more precious sister gold, comes in a range of different alloys. Hallmarks are currently applied to silver at the following standards: 800, 925, 958 and 999 parts per 1000.   There is no obligation on jewellery producers to hallmark silver items that weigh less than 7.78 grams.

Some silver alloys such as ‘Lustre’ a Sterling silver alloy from Carrs of Sheffield and ‘Brilliante’ -which available from a range of manufacturers -  have been developed to be tarnish resistant and are thus a popular choice for cutlery and homewares.

Sterling Silver ‘Sterling’ is the name given to silver that contains 925 parts of silver per 1000.
Britannia Silver ‘Britannia’ is the name given to silver that silver contains 958 parts per 1000.

Platinum

Platinum is one of the ‘noble’ metals and is the most precious of all the metals used for jewellery making.  Platinum standards in the UK are 850, 900, 950 and 999 – making platinum alloys the purest and most hypo-allergenic available.  Platinum is naturally ‘white’ and its, strength, durability, rarity and cost makes it much sought after by those who demand the best.  It has seen strongly increasing sales at the luxury end of the jewellery market over the past ten years.  All platinum jewellery being sold in the UK over 0.5 grams must bear a hallmark.

Palladium

Another precious metal which is being increasingly used by UK jewellery companies is palladium.  This metal cannot at present be hallmarked but it is hoped that the law will be changed to allow this.  Palladium is a platinum group metal which 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 33% less than gold. Being light 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 like platinum it can be highly polished but also works well with a matt finish.

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, watchback 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.

BJA does not recommend 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.