Choosing Gold for Jewellery
24kt gold isn’t typically used in jewellery for a number of reasons. Firstly, it’s very expensive, containing twice as much gold as 14kt, which means it also costs more to produce jewellery with. It does, consequently, have a higher resale value though. It’s also very soft and highly malleable, meaning it doesn’t retain shape well and scratches easily. It also has a bright, orange tone to it which isn’t deemed as attractive as the more creamy tone of gold most people are used to seeing. In the West, this isn’t typically used but tends to be more popular in China where it’s used in traditional wedding jewellery or collectible items.
18kt gold is made up of 75% gold and 25% alloy. 18kt gold is the most typical type used for high quality fine jewellery and luxury watches. It has a desirable, sunny yellow appearance that is deemed classically attractive. Additionally as this gold has a high purity percentage, there is very little risk of skin irritation that can happen when gold is mixed with high quantities of nickel, for example. It is, however, expensive and fairly easy to scratch.
14kt gold is popular for rings and other fashion jewellery in the US and UK. Being 14 out of 24 parts gold, it isn’t quite as bright or saturated as 18k but is cheaper. It does, however, have a larger potential to trigger skin irritation because of a higher alloy content.
Below this, 10kt gold is the most impure it can be while remaining legally “gold” in most countries. Typically, luxury brands don’t offer 10kt gold. It’s used in affordable, highstreet jewellery but is rare for engagement rings and fine jewellery.
Recycled Gold
More and more fine jewellery brands today are deciding to use 18k recycled gold, instead of newly mined. By melting pre-loved pieces down, you can easily reshape gold without it losing its quality, whilst also cutting out the unsustainable mining process. Jewelry is actually one of the only products that can be completely recycled. 18k gold is the most popular choice for fine jewelry as it’s made from a combination of 75% pure gold and 25% alloy (other precious materials), meaning it’s as pure as possible whilst still maintaining its practicality.
When it comes to mining for gold, there’s no better place for it than trawling through old and disused jewellery boxes.
Recycled gold is made from refined precious metals that are sourced from a combination of locations. According to the World Gold Council, recycled gold accounted for 28% of the total global gold supply of 4,633 metric tons in 2020. They found that 90 percent of that comes from discarded jewelry and the rest from electronic waste, like mobiles and laptops. Older cars with catalytic converters and electronics with circuit boards also contain recyclable gold and are sold to be melted down once they’re no longer in use.
Purity Assessment
The process of recycling gold starts by assessing its purity. This is categorised using the karat system, ranging from 10K, 14K, 18K, 22K and 24K. 24 karat gold represents its purest form, meaning that 24 out of 24 parts of the metal are gold. This term may sound familiar to the carat measurement associated with diamonds, however this is a unit of mass used to weigh the material, whereas karat only measures the purity.
How are the quantities of impurities assessed? There are multiple methods:
An acid kit: the cheapest method, these kits come with a black touchstone and several acid solutions, which are marked for different karats. You start by scratching the touchstone with the gold in question, leaving a streak on the stone. Experts will then make a parallel control streak with a piece of gold of the same estimated value. Finally, they'll put a drop of an acid solution on both streaks and compare the reactions.
Electronic tester: a special liquid or gel makes it possible to create a circuit between the device’s probe and gold which then tests the gold’s electrical conductivity. This method is fairly accurate but must be fully cleaned of gel between uses.
X-ray fluorescence spectrometer: the most accurate test, these machines send X-rays through the tested item, exciting the atoms which move into a higher energy state. When they return to their ground state, they release radiation which the machine reads and can figure out what the item is made of.
Melting point test: 24k recycled gold has a melting point of 1,064 degrees Celsius, allowing you to differentiate between other materials.
Once the gold is sorted, it will be melted in a crucible and then poured into bars marked by purity or smelted to remove further impurities. The smelting process either burns impurities off or a flux, usually Manganese Dioxide, is added to react with impurities and separate them from the pure metal.