If you take off a favourite ring, necklace or bracelet and find a green or black mark underneath, it can be alarming. Fortunately, discoloured skin is often caused by a chemical reaction involving the metals in the jewellery, rather than anything being wrong with your skin.
Why does jewellery turn skin green?
Green staining is commonly associated with copper. Copper can be used on its own or as part of an alloy in jewellery. When copper reacts with substances in its environment, corrosion products can form, including the familiar blue-green patina associated with weathered copper.
When jewellery containing copper is worn against the skin, moisture and everyday substances can encourage reactions at the metal's surface. Perspiration, cosmetics and skin products can all play a part. The resulting compounds can transfer onto the skin and leave the characteristic green mark.
This doesn't necessarily mean that a piece of jewellery is poor quality. Precious-metal jewellery is not always made from pure gold or silver; metals are alloyed for reasons including strength, hardness and colour.
Why does jewellery sometimes leave black marks?
Black marks can have several causes.
Silver, for example, reacts with sulphur compounds to produce silver sulphide, the dark coating commonly known as tarnish. Tarnish or other surface deposits can subsequently rub against the skin.
Other metals can oxidise too. Copper oxidation can produce black copper oxide as part of the corrosion process.
Does the type of metal make a difference?
Yes, the metal content of your jewellery can affect how likely it is to react with your skin or substances it comes into contact with.
Interestingly, even very high-purity gold isn't completely immune to visible discolouration. Precious metals such as gold, silver and platinum are generally unlikely to cause an allergic reaction when they are in their pure form. Where irritation does occur, it is often associated with other metals used in the alloy rather than the precious metal itself.
Lower-carat gold and many base-metal pieces, including fashion jewellery, contain a higher proportion of other metals. These may be more prone to reacting with moisture, oxygen and other chemicals. If you're sensitive to a particular metal, it may also increase the likelihood of irritation.
Importantly, though, a green or black mark doesn't automatically mean you're allergic to your jewellery. Discolouration caused by a reaction between the metal and substances such as sweat or cosmetics is different from an allergic skin reaction.
Can cosmetics make jewellery discolour?
They can contribute.
Everyday products including lotions, perfume, hairspray and other cosmetics can contain chemicals capable of damaging or discolouring precious metals. So, if a ring suddenly starts leaving marks when it never did previously, consider whether you've changed your hand cream, skincare products or other cosmetics.
How can I prevent green or black marks?
Keeping jewellery clean and dry may help, as can putting jewellery on after cosmetics and perfumes have dried. Remove pieces before swimming, showering or using cleaning chemicals.
Follow the appropriate cleaning instructions for the particular metal and gemstones, as some gems and treatments require special care.
If your jewellery starts leaving green or black marks, looking after it correctly may help prevent further discolouration and protect its condition. However, not every problem or mishap can be prevented. You may therefore also want to consider jewellery insurance and the cover available for accidental damage, loss and theft.
Further reading:
Does stainless steel jewellery tarnish?
Things that could be damaging your jewellery
Sources
timothyroe.com/blog/why-does-jewellery-turn-your-skin-green-or-black/
assayoffice.co.uk/analytical-services/nickel-testing
gia.edu/gems-gemology/winter-2015-characterization-tarnish-spots-chinese-high-purity-gold-jewelry
