9ct, 14ct or 18ct: which gold your customers will actually ask for

What ct means and what the numbers stamp

Carat (ct) in gold counts the parts of pure gold in 24. A 9ct piece is 9 parts gold in 24, or 37.5%. An 18ct piece is 18 parts in 24, or 75%. Fineness says the same thing in parts per thousand, which is why you see 375, 585 and 750 on the inside of a ring.

14ct is 14 divided by 24, or 58.33%, but the standard fineness grade is 585 (58.5%). A piece that carries a 585 stamp and meets it is a proper 14ct piece. The international standard for jewellery fineness, ISO 9202, has listed 375, 585, 750 and 916 as its gold grades since its 1991 edition. It has been revised since, so check the current edition if you need the full table.

• 9ct = 375 = 37.5% pure gold
• 14ct = 585 = 58.5% pure gold (14/24 is 58.33%, the standard grade is 585)
• 18ct = 750 = 75% pure gold

Stamping and hallmarking in Australia

Australia has no mandatory hallmarking and no government assay office. The guarantee of purity sits with the manufacturer or importer, not an independent body. The relevant standard is AS 2140-2008, Jewellery: Fineness of precious metal alloys, which sets composition and marking requirements. When Standards Australia launched the system in 2008, the trade press reported that articles should carry the metal symbol and the minimum fineness in the millesimal system rather than in carats. So a 9ct piece is stamped 375, even though your customer calls it 9ct.

The law that matters is the general one. Describing a piece as 9ct when it is not is a false representation about its composition and standard under the Australian Consumer Law (section 29), and can be misleading conduct under section 18. For a company, the maximum penalty for a false or misleading representation is the greatest of $100 million (for conduct from 28 March 2026; it was $50 million before then), three times the benefit obtained, or, where the benefit cannot be determined, 30% of adjusted turnover during the breach period. In practice the stamp is a promise your business makes to its customer, and you are relying on your supplier to have kept it.

• Ask your supplier to stamp fineness and a maker's mark on every piece where space allows.
• Ask who is responsible, in writing, if a piece tests under its stamped grade.
• Confirm chains, clasps and findings are the same grade as the piece they are sold with.
• Spot-test incoming stock. A handheld XRF analyser or a testing service will do it.

What Australian customers expect

9ct is the gold many Australian customers know and ask for by name. It tends to set the price expectation for plain chains, studs, huggies and signet rings. The common everyday grade in the United States is 14k, so buying habits and online content that come from there do not map directly onto an Australian shop floor.

18ct is the step up: engagement and wedding pieces, and customers who want a richer colour. 14ct sits in the middle. Treat it as a deliberate middle rung, not a way to fill a gap in the price list.

The trade-offs are simple. 9ct is paler, cheaper per gram and generally the harder wearing of the three. 18ct is richer in colour and softer. By proportion, 18ct holds twice the gold of 9ct (75 divided by 37.5), which is why the price gap per gram is so large.

Quoting a ladder

Quote the same design in all three grades, side by side. Customers and staff then compare gold content, not designs. Keep metal weight in grams on the quote, because a heavier piece costs more for a reason the customer can see.

Gold moves daily, so a ladder needs a validity date. If a supplier's quote has no validity date, the price is an indication, not a price.

• One design code across all grades, so a reorder is a code and a grade.
• 9ct as the entry rung, 14ct in the middle, 18ct at the top.
• State grams, finish, stone weights and whether GST is included.
• State how long the quote holds and how a price change after that is handled.

White gold and rhodium plating

White gold is gold alloyed with white metals. Most white gold jewellery is then plated with rhodium, which gives the bright, mirror-white finish that makes diamonds look brighter. The plating is a very thin layer. It wears, and as it thins the alloy underneath shows through, which is often slightly yellowish. How fast that happens depends on how the piece is worn and on the colour of the alloy underneath. Rings and the inside of bands wear first.

Tell customers at the counter that re-plating is normal upkeep, not a fault. Have a re-plating partner and a price for it. A customer who hears this at the point of sale returns for the service; one who finds out a year later returns for a refund.

Why yellow carries the volume and white earns its place

Yellow gold is the usual choice for everyday plain pieces, and white gold is chosen where the diamonds are the point: bridal rings, tennis bracelets and diamond studs. A white setting lets the stones read as colourless, and customers expect it.

That suggests buying depth by role, not by metal. Hold depth in yellow for plain pieces and in white for stone-set ones. Add the other colours as range extensions once the core sells.

SVN Diamonds is a Melbourne-based supplier of lab-grown diamond and gold jewellery to Australian jewellers. Stock pieces dispatch in 1–2 days, and the catalogue and trade application are on this site.