Metals and gemstones
Sterling silver is 92.5% silver alloyed with 7.5% other metals, such as copper. The added metals make the silver more malleable and suitable for use in jewellery. It is hallmarked 925.
Pure gold is very soft, so it is alloyed with other metals to make it stronger.
18ct gold has 18 parts gold and 6 parts alloying metals in every 24, making it 75% gold. It is hallmarked as 750.
9ct gold has 9 parts gold and 15 parts alloying metals in every 24, making it 37.5% gold. It is hallmarked as 375.
9ct and 18ct gold have a very similar surface hardness and will wear quite similarly over time. As 18ct gold has twice the content of pure gold it is more expensive, but it is also slightly softer. This is why 22ct and 24ct gold are used less in jewellery, as the very high gold content means they can be marked and bent easily.
Rose gold has a higher ratio of copper in the alloys to make it a redder colour.
White gold has a higher ratio of silver and palladium in the alloys to make it a whiter colour.
Due to the different percentage of gold in 9ct and 18ct gold they vary in colour as well as hardness, as shown in the colour comparison lower down this page. 18ct white gold is naturally quite dark, but can be plated with rhodium as described below. You can compare the different colours below.
Palladium is relatively new to the jewellery world and it was only being added to the legal hallmarking act in 2009. It is a member of the platinum family, with a lower density but a similar silvery white colour. It is almost as hard as platinum and is a less expensive choice for a very hard wearing metal. It is also hypo-allergenic, making it ideal if you are allergic to silver and gold.
I use palladium which is 95% pure and alloyed with 5% other metals. It is hallmarked as 950.
Metal hardness can be measured in a few different ways. The Vickers scale tests how much a metal is dented by a diamond. According to the Vickers scale, in order from softest to hardest, are sterling silver, 9ct gold, 18ct gold, palladium then platinum.
The Mohs scale tests how easily the surface of a material is scratched. According to the Mohs scale, in order from softest to hardest, are sterling silver, 18ct gold, 9ct gold, platinum then palladium.
There is also malleability to bear in mind, which will affect how much a ring can be misshapen and squashed with wear. 18ct yellow gold is far more malleable than 9ct yellow gold even though it is harder to dent, so a thicker band is always advised to prevent bending over time.
The alloy of the metal also affects the harness of the metal. For example,18ct white gold is alloyed with palladium to make it whiter in colour, which also makes it much harder than 18ct yellow gold.
So, there is no exact answer to ongoing question of whether 9ct or 18ct gold is hardest. Palladium and platinum are always harder than gold alloys and silver. Palladium is less dense than platinum, so platinum is the most durable metal overall. The best rule of thumb is to always wear the same metal and carat next to each other for even wear over time.
Rhodium is a member of the platinum family. It has a white silver colour, is hard wearing and is also hypo-allergenic. Rhodium is often plated onto silver and white gold to give them a whiter colour like platinum and to prevent the jewellery from tarnishing.
Rhodium plating can wear off over time, especially on rings and when exposed to perfumes, cosmetics and moisture. The plating can be re-applied as needed to keep the piece looking pristine. You should expect to get a ring re-plated once a year.
Most white gold jewellery bought on the high-street is rhodium plated. I personally prefer the warmer tones of the white gold, so I don’t plate my jewellery as standard. However, if you prefer the white finish of rhodium plating just let me know, and I’m happy to apply it.
My gold plated jewellery is sterling silver plated with a layer of 18ct gold. It is classed as Vermeil gold, as the plated layer is at least 2.5 microns thick. A thicker layer is applied to rings as they will experience more wear.
Gold plating can wear off over time, especially on rings and when exposed to perfumes, cosmetics and moisture. The plating can be re-applied as needed to keep the piece looking pristine. A general rule of thumb is that a layer of 1 micron should last a year with moderate wear. So vermeil plating will last at least a couple of years if looked after.
Diamonds are graded by their colour, clarity, carat and cut - known as the 4 Cs.
All diamonds are sourced from ethical and sustainable suppliers to ensure no exploitation such as child labour and dangerous mines are involved. I can also supply diamonds which are fully traced from their mines in Canada, each with their own identifying laser mark, serial number and certificate.
I specialise in using beautiful natural gemstones in my jewellery. There is an amazing range of colours and varieties available to make your jewellery even more special.
All of the stones I use are responsibly and ethically sourced and cut by talented lapidaries.
If you are interested in a particular gemstone, please feel free to contact me for more information.
If you are commissioning a special design I can order in a selection of gemstones so you can handpick the perfect stone.
The surface hardness of gemstones is measured by the Mohs scale. This is a scale of 1 to 10, 10 being the hardest.
If you are choosing a gemstone for an engagement ring, I usually advise a stone with a hardness of at least 8, but preferably 9 or 10. Stones with a hardness of 7 or below will soon show scratches from everyday wear, as 7 is the hardness of silica and most grit and dust that will abrade your jewellery.
For a normal ring, the softer stones are fine though – you just have to be a bit more careful with them.
Here are a few examples of common gemstones used in my jewellery and their hardnesses:
6 - 7. Moonstone, labradorite, opal, peridot, tanzanite, jade
6.5 - 7.5. Garnet
7. Peridot, Tourmaline, Quartz - includes amethyst, citrine, agate, carnelian
7.5 - 8. Emerald, aquamarine, spinel.
8. Topaz, cubic zirconia.
9. Sapphire, ruby.
However, the scale is non-linear. For example, sapphire is two times harder than topaz, and diamond is four times harder than sapphire.
Some gemstones are quite delicate and need a little extra TLC. Some stones have a good surface hardness but are very brittle and chip easily, such as tanzanite and emerald. The brilliant colours of an opal are created by light refracting through water inside a spherical crystal structure. For this reason, an opal should never be submerged in water, exposed to direct heat or chemicals/cosmetics, as this can cause the opal to go cloudy, dull and even crack. But the amazing colours of an opal are well worth the extra effort!