18K Gold
Gold that is 75 percent pure, hallmarked as 750 and valued for durability in stone set jewellery.
18K gold is 18 parts pure gold to 6 parts other metals, which comes to 75 percent gold and the hallmark 750. That extra quarter of alloy buys real strength, which is why 18K is the standard for diamond and gemstone jewellery that has to grip stones tightly and survive years of wear. It also gives designers a colour palette: change the alloy metals and the same 75 percent gold becomes yellow, white or rose while keeping the identical purity.
Why 18K suits stone set jewellery
Holding a diamond securely means thin claws and prongs that take constant knocks. At 75 percent gold, 18K is markedly harder than 22K, so those claws hold their shape and keep the stone safe over time. That balance of good gold content with practical durability is why most fine diamond rings, tennis bracelets and pave pieces are made in 18K.
The 750 hallmark certifies the 75 percent purity, and the purity fraction 0.75 is used directly in pricing. A 6 gram 18K ring contains 4.5 grams of pure gold, so its metal value is 6 times 0.75 times the 18K gold rate, before the stones, making charge and taxes are added.
- 18K is 75 percent pure gold, hallmarked 750.
- The purity fraction is 0.75.
- Harder than 22K, so it holds stones securely.
- 6 grams of 18K contains 4.5 grams of pure gold.
One purity, three colours
Because colour comes from the alloy rather than the gold itself, 18K is made in yellow, white and rose while staying exactly 75 percent gold. Yellow 18K uses copper and silver, rose 18K leans on more copper for its pink tone, and white 18K uses palladium or nickel and is usually finished with rhodium plating for a brighter white.
This is a useful selling point: a customer choosing between colours is not choosing between purities. An 18K white gold ring and an 18K yellow gold ring hold the same amount of gold and the same metal value, so the decision is purely about look and, for white gold, the ongoing rhodium plating.
- 18K gold is 75 percent pure and hallmarked 750.
- Its added strength makes it the standard for stone set jewellery.
- It is made in yellow, white and rose at the same 75 percent purity.
- The purity fraction 0.75 sets its metal value in pricing.
18K Gold, in short.
What does 750 mean on gold?
750 is the hallmark for 18K gold, showing it is 75 percent pure gold in parts per thousand form. The remaining 25 percent is alloy metals added for strength and colour.
Is 18K gold better than 22K?
Neither is simply better. 18K is harder and holds stones more securely, so it suits diamond jewellery, while 22K has more gold and a richer colour, so it suits traditional and bridal pieces.
Does white and yellow 18K gold have the same purity?
Yes. Both are 75 percent gold. Only the alloy metals differ, which changes the colour, not the gold content or the metal value for the same weight.
Related terms
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