FSS Jewellery · Solid Gold
9K, 10K, 14K, 18K
Which Gold Should You Buy?
The number stamped inside your jewellery is a promise. Here is what it actually promises.
"Pure gold is too soft to hold a shape. Every piece of jewellery you have ever loved was a compromise — and the karat number tells you exactly which compromise was made."
THE SHORTHAND
A karat is a fraction,
not a grade
There is a persistent belief that 18K gold is better than 14K, and 14K better than 9K. It is not quite wrong, but it is the wrong question. Karat measures one thing only: how much of the metal is gold, expressed in twenty-fourths. Pure gold is 24 parts of 24. Everything below that is gold plus something else — usually copper, silver, zinc, sometimes palladium.
That something else is not filler. It is structure. Pure gold has a hardness of about 2.5 on the Mohs scale, roughly that of a fingernail. A ring made of it would deform in the pocket of your coat. The alloy is what allows gold to be drawn into a chain a millimetre wide and survive a decade of being pulled over your head.
So the honest framing is a trade. More gold means deeper colour, greater density, higher intrinsic value — and a softer metal. Less gold means a harder, more scratch-resistant piece with a paler, cooler tone. Neither end of that scale is correct. What is correct depends entirely on what you intend to do with the piece.
The four karats, at a glance
9K — hallmark 375
37.5% gold · AU375
10K — hallmark 417
41.7% gold · AU417
14K — hallmark 585
58.3% gold · AU585
18K — hallmark 750
75.0% gold · AU750
Hardest wearing
9K and 10K
Richest colour
18K
Most balanced
14K
All four
Solid gold — never plated
Those three-digit numbers are not marketing. They are fineness marks, expressed in parts per thousand, and in the United Kingdom they are struck by an independent Assay Office rather than by the maker. Gold articles above one gram must legally carry one. When you see 585 stamped on a clasp, a third party has verified the claim.
THE MATERIAL
What the other
percentage actually is
Gold purity at a glance
Select a karat
Copper warms the tone and adds hardness — it is why rose gold is rose. Silver cools it and softens the metal slightly. Zinc lowers the melting point and helps the alloy flow into fine detail during casting. Palladium or nickel whitens it, which is how white gold is made. Reputable makers do not use nickel; a meaningful proportion of people are sensitised to it, and the reaction is unpleasant. Every FSS piece is nickel-free, across all four karats.
Here is the consequence that matters at the counter. Solid gold, at any karat, does not tarnish, does not flake, and does not expose a base metal underneath, because there is no base metal underneath. Gold-plated jewellery is a microns-thin layer of gold over brass or silver. It will wear through. The distinction between 9K and 18K is a matter of degree. The distinction between 9K and gold-plated is a matter of kind. If you would like to understand where the raw material comes from before it ever reaches an alloy, we wrote about that in how gold is mined, refined and turned into fine jewellery.
One geographic quirk is worth knowing if you shop internationally. In the United Kingdom, 9K is legally gold and has been for over a century — much of the country's antique jewellery is 9ct. In the United States, the legal minimum for anything sold as "gold" is 10K. The same necklace, honestly described, cannot be called the same thing on both sides of the Atlantic. Neither jurisdiction is lying. They simply drew the line in a different place.
WHAT MAKES IT EXCEPTIONAL
Six things to weigh
before you choose
Colour depth
18K reads unmistakably yellow. 9K reads pale, almost champagne, in daylight.
Hardness
Lower karats resist scratching better. This matters most for rings and bracelets.
Where it sits
A necklace hangs. A ring is struck against desks and door handles. Choose accordingly.
Skin sensitivity
Higher gold content means less alloy. Nickel-free at every karat, always.
Intrinsic value
18K holds roughly twice the gold of 9K by weight. The price reflects the metal.
Intention
Worn daily for a decade, or kept for a daughter? The answer chooses the karat.
Notice what is absent from that list: quality of craftsmanship. A poorly made 18K chain will fail before a well-made 9K one. Karat describes the metal, not the maker.
HOW TO CHOOSE
Three ways of
arriving at an answer
If the piece will not leave your body — the chain you sleep in, the hoops you forget you are wearing — choose for endurance rather than richness. 9K and 10K take knocks with indifference. The colour is quieter, which is often the point: a pale gold reads as restraint rather than ornament, and layers under a shirt collar without announcing itself.
- The Double Chain Hoop in 9K — the earrings you put in on Monday and forget by Friday
- The Dainty Sparkle Chain in 10K — diamond-cut links, hard enough for daily wear
- Rings and bracelets take the most abuse of any jewellery. Bias downward in karat
A gift carries a second requirement beyond the object itself: it must be legible as significant. Here 14K is almost always the right answer. It is visibly, warmly gold — nobody mistakes it for plated — while remaining a piece the recipient can wear immediately and constantly rather than storing for occasions that never come.
- The Butterfly Earrings in 14K — cubic zirconia across the wing, substantial in the hand
- 14K is the international default. It reads correctly in every market you might post to
- Buy the karat she will wear, not the karat that sounds most impressive
Some pieces are bought once. An anniversary, a birth, a piece intended to outlive the person choosing it. Here the calculus inverts: softness stops being a liability, because the piece will not be worn hard, and the depth of colour and weight of gold become the entire point. 18K has a density you can feel across the palm.
- The Thin Box Chain in 18K — square-section links, a flatter and more deliberate line
- The Dainty Sparkle Chain in 18K — the same design, in the richest metal we offer
- Higher karat gold is easier for a jeweller to repair and resize decades from now
THE EDIT
Your questions,
answered
- AU — the chemical symbol for gold, from the Latin aurum.
- 585 — the fineness, in parts per thousand. 585 of every 1,000 parts are gold.
- 585 ÷ 1000 × 24 = 14.04 — which is where 14K comes from.
By the same arithmetic: AU375 is 9K, AU417 is 10K, AU750 is 18K.
Care & keeping
Warm water, mild soap
Solid gold needs nothing exotic. A soft brush, warm water, a drop of unscented soap, then dry fully.
Fragrance last, jewellery after
Perfume, hairspray and lotion dull the polish over time. Let them dry before the gold goes on.
Store softly, store apart
Gold scratches gold. A pouch each, particularly for 18K, which is the softest metal in the range.
Remove for chlorine
Solid gold is water-safe. Chlorine and bleach attack the alloy metals, not the gold. Take it off.
Solid gold, four ways
Choose the metal.
Keep the piece.
Every FSS piece is solid gold — 9K, 10K, 14K or 18K, hallmarked and nickel-free. Never plated, never filled. Explore the full collection and find the karat that belongs to your life. Free worldwide delivery on orders over £100, or local equivalent.
Shop the Sparkle Chain