More About Precious Metals
When deciding on your wedding or engagement ring it is important to consider the materials that it is made from: what are the positives and negatives of the various metals available?
Gold is the most popular choice for wedding and engagement rings for both men and women. Attractive, easily worked and resilient, it has been used in jewellery for thousands of years.
The natural element is found in igneous rocks and associated quartz veins often in small quantities invisible to the naked eye. It is also concentrated in river deposits as nuggets or grains. Gold was traditionally panned from these fluvial deposits but modern commercial mining involves large earth-moving machinery and chemicals for processing the ore. The main sources of gold are Africa, the Americas, Russia and Australia.
When choosing gold, carat and colour should be considered:
The carat is a measurement of the purity of the gold. Pure gold is 24 carats, which is the most valuable; however pure gold is very soft, so alloys are added which change its properties, adding to is hardness and strength.
Common carats are 9, 14, 18 and 22, although other countries may use slightly different purities. Gold is hallmarked to tell you its purity.
9ct gold = hallmarked with 375 (meaning it is 37.5% pure gold)
18ct gold = hallmarked with 750 (meaning it is 75% pure gold)
Hardness and durability are important factors to consider when buying an engagement or wedding ring which will be worn everyday. 22 or 24ct are usually considered to be too soft for this use. Surprisingly, there is negligible difference between the hardness of 9 and 18 ct gold, so when deciding between these carats, hardness can be disgarded and only colour and value need be considered.
In general, 18 is considered the best carat to use for wedding and engagement rings as, compared to 9ct, it wears better over time and keeps its lustre and colour. Although more expensive, most people want something as special as 18 carat gold for such a significant purchase.
White Gold and Yellow Gold
The colour of gold is determined by the mix of alloys used.
Yellow gold is the most popular, being closest to the element's natural colour. Pure gold is a natural yellow colour, but this is altered when alloys are added. Alloys such as copper and zinc are added to increase gold's hardness and durability, and the more of these that are added - such as, in 9 carat gold, the less rich the gold colour will be.
White gold is the second most popular colour. This is achieved by mixing alloys such as silver or palladium with pure gold, to whiten it. Traditionally nickel was used, however this is no longer the case as it can cause an allergic reaction in some people. White gold is then normally coated with Rhodium to make it even whiter, as without it, it is in fact a pale grey colour. Rhodium is a precious metal in its own right, in the same family as platinum and shares many of its properties including its white colour. Because of this plating, the white lustre of white gold can fade over time as it wears and therefore should be replated every 2 to 3 years.
Other favourite colours include rose or red gold. It is possible to have a combination of colours in a ring.
Platinum is the rarest and most expensive of all precious metals, 30 times rarer than gold, with an iconic status and a strong emotional appeal. To put it in perspective, if all the platinum ever mined were poured into an olympic sized swimming pool, it would scarcely cover the ankles! In comparison gold would fill three pools to the top. A platinum ring will be around three times as expensive as an 18ct gold ring.
Platinum forms in igneous rocks often as ores in which grains are too small to be seen with the naked eye. It may also occur in river deposits. It is rarely found as nuggets.
It has been used for thousands of years but it was not until the 1920s that the technology was developed to achieve the temperatures needed to manipulate the metal. Part of its value is linked to the high level of craftsmanship required to make platinum jewellery, as well as its rarity.
Platinum is the metal of choice for setting the world's most famous gemstones such as the Star of Africa and the Hope Diamond. Its pure white lustre, brings out the true radiance of diamonds. It is also a very dense and durable metal, 40% heavier than gold and highly resistant to corrosion and tarnishing. It doesn't change shape or wear away and thus holds stones firmly in place. It never loses its lustre unlike white gold which can fade in time and may require replating; and although it is possible to scratch as with all metals, it is by far the most resistant.
Platinum jewellery is 95% pure, which adds to its appeals for something as special as a wedding ring. 18ct gold, in comparison, is 75% pure. Platinum is also hypoallergenic, making it ideal for sensitive skin.
Titanium is a whiteish-grey metal, the hardest metal on the planet, it is three times stronger than steel yet extremely light weight. Pure titanium is 100% hypoallergenic so can be worn by people with sensitive skin. It is a popular choice for men's wedding bands and is a good choice for people in manual jobs as the metal is resilient to being bent and scratched. It is possible to combine titanium and another metal such as white gold to create a two tone band.
Titanium cannot normally be resized which is an important consideration, however it is possible to exchange your ring for a different size if needed.
The hallmark comprises a minimum of three symbols:
- The sponsor or maker's mark which is a registered mark of the maker or sponsor of the piece.
- The purity of the metal - the number indicates the percentage of pure metal. A gold ring with 375 marked in it indicates that it is 37.5% gold, or 9 carats (9 parts out of 24 are gold, or 37.5%). A gold ring with 750 marked on it indicates that it contains 75% gold, or 18 carats (18 parts out of 24). A platinum ring with 950 marked on it indicates 95% platinum.
- The Assay Office mark - which is the mark of the official office that has tested the metal's purity - London, Birmingham, Sheffield or Edinburgh in the UK.
See also our guide to diamonds