The karat scale: purity in twenty-fourths
Karat expresses how much of an alloy is gold, as a fraction of 24. Pure gold is 24 karat; a 9K alloy is nine parts gold and fifteen parts other metals. The remainder is other metals, which may include copper, silver, or zinc. The gold content is the main basis of a gold-buying offer.
One warning about the terminology: in American usage, karatwith a K measures gold purity. Carat with a C, when applied to gemstones, is a unit of weight (0.2 grams), not purity. A “2-carat diamond” is describing the stone's weight, not the gold around it.
Millesimal fineness: the same truth in thousandths
Modern marks usually state purity in parts per thousand. The mapping to karats is fixed and worth knowing by heart, because the number stamped inside your ring band is almost certainly one of these:
| Karat | Fineness | Gold content |
|---|---|---|
| 24K | 999 | Pure gold — 99.9%+ |
| 22K | 916 | 22 parts in 24 — 91.6% |
| 18K | 750 | 18 parts in 24 — 75.0% |
| 14K | 585 | 14 parts in 24 — 58.5% |
| 9K | 375 | 9 parts in 24 — 37.5% |
A ring stamped 750 and a ring sold as 18K are making exactly the same claim. Continental jewelry leans on the millesimal numbers; older British pieces often carry the karat figure alongside. Silver uses the same system — sterling is 925, and continental grades such as 800 and 835 are common in inherited cutlery and tableware.
Hallmarks: the claim, witnessed
A hallmark is a set of marks struck into a piece recording its fineness — and, in full hallmarking systems, the assay office that tested it and the sponsor who submitted it. Look inside ring bands, on clasps and jump rings, on the reverse of pendants, and near the rims of cups and candlesticks.
Plenty of genuine gold carries no hallmark at all. Marks wear away with decades of skin contact; pieces made before marking requirements, or in countries where marking is not customary, never had them; and small items are often exempt below certain weights. An unmarked piece is therefore not a red flag — it simply means fineness must be established by examination rather than read off the metal. The reverse caution also applies: a stamp is a claim, and claims are tested. Worn marks misread, plated pieces imitate solid ones, and occasionally a stamp is simply wrong.
How purity is actually verified
The trade has a ladder of tests, ordered by how much they disturb the piece. Reading the hallmark under magnification is the first step. Density checks exploit gold's unusual heaviness. Touchstone and acid testing read how the alloy responds at the surface. Electronic and X-ray fluorescence instruments estimate composition without marking the piece at all. Serious assessment combines methods rather than trusting one, because each has blind spots — and plating is specifically designed to fool the quick look.
Troy weight: why your scales disagree
Precious metals are weighed in troy ounces. One troy ounce is 31.1035 grams — roughly ten per cent heavier than the 28.3495- gram avoirdupois ounce used for everyday goods. This is the single most common source of confusion at any counter: two people quote “an ounce”, mean different units, and believe they disagree about the metal when they only disagree about the dictionary. Kitchen scales also drift and round; trade scales are calibrated and read to fractions of a gram. When your reading at home differs slightly from the counter reading in front of you, the unit and the instrument are almost always the explanation.
The gram sidesteps the whole problem, which is why itemized assessments usually speak in grams: a stated weight in grams, times a fineness, times a per-gram reference, times the buying rate, is arithmetic anyone can check on their phone.
What is deliberately excluded from the weight
An item’s total weight may include stones, steel springs, and other non-gold components. Clasps and solder may also contain gold, sometimes at a different purity. We assess the materials and explain any weight deductions used in calculating your offer. What that assessment looks like in practice, stage by stage, is covered in how it works; what each category of item is assessed for is in what we buy.
Spot price and the buying rate
We explain the assessed metal weight, purity, market reference, and buying rate used to calculate your offer, including any deductions.