Jewellery Purity: Karats and Fineness

Karats and fineness are the same fact, written twice

Karat is a fraction out of 24: 22K gold is 22 parts gold to 2 parts other metal. Fineness writes that fraction as a decimal, and it is the form arithmetic needs. 22 ÷ 24 = 0.9166, which the trade rounds to 0.916 and stamps as "916".

Silver is quoted directly as parts per thousand, so the stamp and the fineness are almost the same number: 999 silver is 0.999 fine, 925 sterling is 0.925 fine. Silver is a different metal with a different scale, and a silver fineness has no meaning on a gold item — a point that matters more than it sounds, because a system that lets the two mix will produce fine weights that are arithmetically valid and physically impossible.

Why purity is a number on the item, not a word in the description

Purity is the multiplier in every fine weight the business holds. If it lives in a description field — "22ct", "916 hallmark", "twenty two" — then no total can be computed from it, and the shop's stock figure is a count of pieces again.

Purity and price are two different things

The rate board quotes a price per gram or per tola for a stated purity — in Nepal, typically 24K fine gold and 22K, with silver quoted separately. Pricing a 22K piece therefore means applying the 22K rate to its net weight, not applying the 24K rate to its fine weight and hoping the two agree. They do not, because the making charge, wastage and the shop's own margin sit on top of the metal, and each is agreed on its own basis.

See gross weight vs net weight for which weight the rate is applied to, and today's Nepal gold and silver rates for the figures themselves.

Hallmarks

A hallmark is a stamp asserting purity, applied by an assaying authority rather than by the seller. What a hallmark means in law, and which pieces must carry one, is set by the jurisdiction the shop trades in — for Nepal that is a matter for the relevant government authority rather than for a software vendor, and a business should take its obligations from the official source rather than from a guide like this one.

What a record-keeping system can do is store the purity as a fact about the item and keep it with the piece from purchase through to sale, so the figure on the tag, the figure on the invoice and the figure the stock total was computed from are the same figure.

Old gold: the purity you did not choose

A customer bringing old gold in part-exchange hands the shop a piece whose purity nobody at the counter decided. It might be stamped, it might be stamped wrongly, and it might be a piece made two generations ago to a standard nobody local uses now. Whatever is agreed, the shop is buying metal on a purity assessment, and that assessment is the figure the whole transaction turns on.

Two things follow for the record. The first is that the assessed purity belongs to that piece and not to the category it resembles: old gold taken in at 20K does not become 22K stock because it sits in the 22K tray. The second is that the piece's fine weight is derived from the purity actually assessed, so a shop that records the assessment honestly can reconcile its metal even when a month's intake is a mixture of standards. A shop that rounds every exchange up to 22K for convenience has a stock figure that drifts in one direction, month after month, and no way to find out why.

Where old gold is melted rather than resold, the melt is a movement in its own right: a quantity of assessed fine weight in, a quantity of refined metal out, and a difference that is a real loss rather than a bookkeeping one.

What a shop should record

• The metal. Gold and silver are separate scales; an item's purity has to belong to its metal.
• The purity, as a stored value with a fineness. Not free text.
• The fineness used. Shops differ on whether 22K is 0.916 or 0.9167; what matters is that one figure is used consistently and is visible.
• Fine weight, derived. Computed from net weight and fineness rather than typed, so it cannot drift away from the two figures it comes from.

How DataJewellers handles purity

Purities are set up per metal, each with its fineness, and an item takes a purity that belongs to its own metal — a gold item cannot be given a silver fineness. Fine weight is derived from the item's net weight and that fineness every time either changes, so the stock total and the item record cannot disagree.

Gold is kept in karats, the way the trade quotes it, and silver in parts per thousand. They are not merged into one list, because they are not one scale.

Questions

Is 916 the same as 22K? Yes. 916 is the fineness stamp for 22 karat gold: 22 ÷ 24 = 0.9166.

Why is 24K stated as 0.999 rather than 1.000? Refined gold is not perfectly pure. 999 — "three nines" — is the standard fine-gold grade, and using 1.000 would overstate every fine weight in the shop.

Can one item have two purities? Not as one record. A piece combining gold and silver, or two golds, is recorded as its components if the business needs the metal totals to be right.