An important thing to consider when choosing or commissioning jewellery is the durability your chosen gemstone. You want to make sure that it won’t chip of crack too easily – right?
Gemstone durability is especially important when considering a bespoke engagement ring or wedding ring where the gemstone possibilities are endless. However some stones are soft and just not suitable for everyday wear.
When gemmologists talk about the durability of a gemstone, they are referring to its ability to withstand wear, temperature and chemicals. There are three different aspects that make up the gemmological definition of durability and those are
There are also other important aspects that affect the durability of your gemstone jewellery and these include
This aspect of durability is banded about all over the internet advertised as the way to know whether your gemstone is going to wear well. However hardness it is also one of the most widely misunderstood aspects of gemmology. Hardness is a only measure of how one material can be scratched by another material which is certainly not the whole story when it comes to durability and how your gem will wear.
When it comes to gemstones, we measure hardness using Moh’s scale of hardness. To form this scale, Moh went through various stones and scratched one material with another and then organised his findings into a numerical line showing which ones could be scratched by the others. So if something could scratch everything else (diamond) it received the top ranking, if sapphire (corundum) could scratch everything except a diamond, it came next etc.
Also the Moh’s scale is not linear which can be very confusing and misleading. You can see a good diagram of the Moh’s scale here on the GIA’s website:- http://www.gia.edu/aquamarine-care-cleaning. Diamond is only 1 numerical step away from sapphire (corundum) on this chart which might make you think that sapphire is only slightly less hard than diamond, but as you can see by the exponential shape of the chart, diamond is actually considerably harder than sapphire.
Remember, just because a gemstone is hard, it does not mean that it will be durable or survive heavy wear.
This is the measure of a gemstone’s ability to resist cleavage or fracture. This means how likely it is to be chipped or broken. In my opinion, this is a much more important factor than hardness when choosing a ring to be worn all of the time. As we know from the hammering our fingernails and hands get with everyday use, we want our engagement ring gemstone to resist chips and breakage as much as possible. However there is no nice scale that I have found that lists the toughness of each gemstone.
The toughest gemstone is jade, but this is not the hardest gemstone. This is why jade can be beautifully carved by hand into all sorts of shapes relatively easily (it isn’t that hard)– but if you drop it, it isn’t all that likely to shatter compared to other gemstones (because it is very tough).
Diamond is a good choice for an engagement ring and it is fairly tough but certainly not unbreakable. Over the years we have had a few customers who have managed to chip or split their diamonds. One dropped a washing machine on their finger (I think the diamond saved her finger...but did fracture in the process!). Another customer managed to chip their diamond when she banged her ring on a metal filing cabinet. I guess this should not be surprising – after all you can cleave a diamond when cutting it with steel if you know what you are doing (although usually diamonds are cut with other diamonds). However, it is often surprising for people to learn that if you catch a diamond at the right (or wrong) angle, it can fracture.
Some of the gemstones that we don’t find very tough include emerald, tanzanite, tsavorite, opal and paraiba. So we always warn people who want to use these gemstones in their engagement rings to be very careful with them. It is vital to seek an expert opinion from a very experienced bespoke jeweller as to how tough your choice is likely to be so that you can ascertain whether this will suit your lifestyle.
This is the measure of a gemstone’s ability to withstand temperature and chemicals. Some stones, for example, are very effected by strong temperature and radiation (eg sunlight) and their natural colour can fade. For example white diamonds have good colour stability but some types of chalcedony, amethyst and yellow amethyst can sometimes change colour relatively easily in natural light.
When we resize rings, we have to heat them up to a high temperature in order to re-join the metal. Diamonds and rubies can usually be heated up with a jeweller’s blow torch without any problem as long as the jeweller allows the temperature to come down again gradually. If you heated up a diamond in this way and then quenched it in cold water, the diamond would shatter with the thermodynamic shock. Other gemstones can’t be heated at all (eg opals).
Heating gemstones up can effect some gemstones very badly and this has to be kept in mind when thinking about a bespoke engagement ring which will probably have to be resized a couple of times in a lifetime. For example colour treated diamonds would lose their colour if headed up by a jeweller’s blow torch. Another example, blue topaz, has been heat-treated to achieve the blue colour and this colour can be lost on re-heating. Some organic ‘gemstones’ like amber and peals cannot be heated at all.
Chemical stability can be important for your bespoke engagement ring as can how your gemstone will react in your daily environment. For example emeralds, pearls and opals can be negatively affected by ordinary water (well actually often by the impurities in our water). With emeralds, re-oiling can rectify this. If you plan on wearing your engagement ring when you wash your hands or use hand cream, this should be a consideration.
(4) Gemstone cut
The shape and type of cut of your gemstone can also affect how well it will wear. The “pointier” cuts can be particularly vulnerable on those points which will be weaker parts of the crystal. So corners of a square shaped garnet will be more vulnerable than the side of a round one. For example, we have set round Paraiba tourmalines into engagement rings with no problem but had terrible problems with a pear shaped Paraiba tourmalines which chip very easily at the point.
When I look at gemstones in well worn antique jewellery, the facets or surface of the stones can be quite mottled and worn (even with hard stones like rubies over 1 lifetime). This tends to be more noticeable on faceted stones than it is on smoothly cut cabochon stones. But in any cut, any gemstone will become weathered away by wear over many years. However most stones can be relatively easily re-polished by a lapidarist (via your jeweller), but this usually does require removing them from the mount first which can involve more work than you might think. We really enjoy reworking inherited jewellery for our customers where they have a rather opaque looking scratched sapphire and don’t realise how beautiful it will look once we have re-polished it bringing it back to its glory and set it for them in their melted and reformed and redesigned piece.
Some gemstones seem to be more durable in larger pieces, perhaps something to do with how the crystal structure behaves in impact – I’m not sure. We have particularly noticed this with peridot and garnet. It seems to wear fairly well in a larger stone but small 2mm invisibly set peridots or garnets seem very vulnerable to chips/splits.
(5) Quality and type
The exact type and quality of a gemstone will also affect its properties considerably. For example a piece of ruby matrix (which is ruby within the base rock) is nothing like as durable, beautiful or valuable as a pure piece of ruby crystal – but a layman or a less transparent jeweller might legitimately call both ‘ruby’. A moonstone which is full of striations (eg a white slightly opaque rainbow moonstone) will be much less tough than a piece of pure fine blue moonstone (which look like pure strongly blue-iridescent raindrops) which has been cut from one layer of the feldspar without cutting across several layers. This is because these layers cause planes of weakness in the stone.
With a diamond, a white diamond of good clarity with no natural surface blemishes will stand up to every day wear much better than a grey or black diamond which get their colour from impurities in the stone. These impurities and blemishes effect the durability of the diamond crystal. It won’t be like butter or anything – but will not be as tough as a white one. This is one of the reasons why grey or black diamonds are so much cheaper than clear white diamonds or other coloured diamonds.
(6) The setting
The other thing that is crucial to the wearability of your gemstone jewellery is how it has been set as the setting can either protect it or leave it vulnerable to damage. This is where you need to rely on the skill of a good jewellery designer who will hopefully have taken this into account in their design. However there are lots of different designs out there, some designed for ladies who lunch, and others for those of us with a more active lifestyle – and you may not know which one has been designed for your needs.
Some gemstones which are more durable such as diamonds and sapphires can usually cope with being set in an open sided setting where the girdle (or edge) or the stone is out on show. Other stones like opals or emeralds would easily sustain damage if they are set like this and it is sometimes better to all-around set brittle stones (as long as your jeweller is skilled enough to do this with a brittle stone).
There are also aspects of metal knowledge to consider too which I know isn’t what this blog is about. For example some metals are stronger than others – platinum stays put pretty well and we can make really intricate and delicate looking stone settings from it which are still relatively strong. However exactly the same design in silver would be more effected by wear and those claws may move more easily leading to the loss of your gemstone.
Some customers ask us to make very slim eternity rings that are only the same width as the gemstones themselves. We can physically do this of course but do remember that if you do this, your gemstones will be much more vulnerable to chipping or falling out than if you have a metal border of just half a millimetre each side.
There is quite a lot more than I have noted here to this category and once again, it is best to consult an expert to see if your gemstone setting style will be appropriate for your lifestyle. So please do take the advice of an experienced jewellery designer if they tell you something will be vulnerable – if you go against their warning will have problems with your jewellery - we do usually know what we are talking about!