15ct and 12ct gold explained: 15, 625, 12, .5

If you have ever spotted a piece stamped ‘15ct’, ‘12ct’, ‘625’ or ‘0.5’ and wondered what it means, you are looking at a little slice of antique jewellery history.

In modern jewellery, you are most likely to see 9ct, 10k, 14ct/14k and 18ct gold. High carat gold such as 22ct is still used, but less frequently (probably due to the high cost of gold in the 21st century). In the UK and in many antique pieces found in Australia, two additional gold standards were widely used up until the 1930s: 15ct gold and 12ct gold.

15ct and 12ct were used by some makers from 1854 to 1932 - so these purities are a great clue to help assess age. Both were replaced by 14ct in 1932 but are still highly sought after for their age, beauty and collectibility.

What are 15ct and 12ct gold?

Both 15ct and 12ct gold are real gold, of differing levels of purity.

• 15ct gold = 62.5% pure gold (often stamped ‘15ct’ or ‘625’)
• 12ct gold = 50% pure gold (often stamped ‘12ct’ or ‘.5’)

15ct gold Most often seen in antique English and Australian pieces, 15ct gold (625 or 62.5% pure) is a favourite with collectors - and for good reason. Slightly above 14ct, but below 18ct, 15ct occupies a special place in our hearts. Often rosier in colour (but with some beautiful true yellow gold exceptions!), 15ct glows with a subtle shine usually matched with a lovely patina due to its age. Used for everything from rings through to chains and pendants, 15ct gold is a lovely and versatile choice for everyday wear.

12ct gold A rare gold carat, 12ct (0.5 or 50% pure) is seldom seen even in the antique jewellery community. We’ve only ever had two 12ct pieces: one with full English hallmarks and the other with Australian pseudo hallmarks. 12ct gold appears to have been used primarily in antique English and Australian jewellery, and was eclipsed by the popularity of 9ct gold (which was introduced in the same year as 12ct and 15ct). 9ct gold is commonly used to this day in Australia and England.

Is 15ct worth more than 14ct?

By pure gold content, 15ct contains slightly more gold than 14ct (62.5% vs 58.5%).
But in real world antique jewellery pricing, value is usually driven by:

• The piece itself (design, craftsmanship, condition)
• Rarity and desirability
• Gemstones and period
• Provenance and maker when known

In other words: collectors often pay a premium for 15ct because it is both beautiful and period-specific, not just because of the gold percentage.

Why collectors love 15ct and 12ct

Whether you’re drawn to the soft glow of 15ct or the genuine rarity of 12ct, these gold standards are part of what makes antique jewellery so special. They’re a quiet clue to age and authenticity, and a reminder that the best pieces carry both beauty and history - made to be worn, loved, and collected.

Ready to find a new piece for your collection? Check out our full range here.