Most purity checking is reading, not testing. A hallmark on a modern piece tells you the karat, who assayed it and — in India — carries a code you can verify in an app. The home tests exist for the cases where there is no hallmark to read: inherited jewellery, unmarked pieces, or anything bought informally.
Step 1: read the hallmark
Fineness is stamped in parts per thousand. Learn six numbers and you can read almost any piece:
| Stamp | Karat | Gold content | Value per gram |
|---|---|---|---|
| 999.9 | 24K | 100.0% | Rs 40,264.63 |
| 916 | 22K | 91.7% | Rs 36,909.26 |
| 875 | 21K | 87.5% | Rs 35,231.55 |
| 833 | 20K | 83.3% | Rs 33,553.84 |
| 750 | 18K | 75.0% | Rs 30,198.47 |
| 585 | 14K | 58.3% | Rs 23,487.69 |
| 417 | 10K | 41.7% | Rs 16,776.94 |
The stamp is usually inside a ring band, on a clasp, or on the inner edge of a bangle. It is small — a phone camera in macro mode or a cheap 10x loupe makes it readable.
What a hallmark should include
- In India: the BIS mark, the purity grade written as "22K916" or "18K750", and a six-digit alphanumeric HUID. The HUID is verifiable in the BIS Care app — if it does not resolve, treat the piece as unhallmarked.
- In Pakistan: hallmarking is not universally mandated, so a stamp is often the maker's own mark rather than an independent assay. Trusted jewellers issue a purity certificate with the invoice; that certificate, not the stamp, is what carries weight at resale.
- In the Gulf and UK: assay office marks are standard and reliable. UK pieces carry a sponsor's mark, a fineness number and an assay office mark.
A number stamped without any accompanying assay mark is a claim by the maker, not a certification. That does not make it false — most are accurate — but it is not independently verified.
Step 2: the tests that actually work
Density test — the most reliable at home
Gold's density is 19.32 g/cm³, far higher than almost anything used to imitate it. You need a kitchen scale accurate to 0.1 g and a container of water.
- Weigh the piece dry. Call this W.
- Suspend it fully in water on a thread, without touching the container, and record the apparent weight. Call this W₂.
- Density = W ÷ (W − W₂).
A result near 19.3 indicates 24 carat. Around 17.7–17.8 is consistent with 22 carat, and roughly 15.5 with 18 carat. A result under 14 means the piece is substantially not gold. The test cannot detect a tungsten core — tungsten has almost identical density — but tungsten-cored fakes are a bullion bar problem, not a jewellery one.
Magnet test — useful in one direction only
Gold is not magnetic. If a piece is drawn to a strong magnet, it contains a significant ferrous core and is not solid gold. But brass, copper, lead and aluminium are not magnetic either, so passing this test proves nothing on its own. Use it to rule out, never to confirm.
Visual and wear inspection
- Check high-wear points. Plating wears through first at clasps, ring undersides and chain links. A different colour showing through is conclusive.
- Look for discolouration on skin contact. Real gold does not tarnish or leave green marks. Heavily alloyed or plated pieces often do.
- Weigh it against its size. Gold feels noticeably heavier than it looks. If a substantial piece feels light in the hand, weigh it properly.
Step 3: when to stop and go to a professional
For anything of real value, a jeweller with an XRF analyser will read the exact composition in seconds without marking the piece, and most do it free for walk-ins. That is the correct answer for inherited jewellery, for anything you are about to sell, and for any piece where the home tests disagree with the stamp.
Acid testing works and kits are widely sold, but it scratches the piece, involves corrosive acid, and depends on judging a colour change correctly. It is a trade tool used on scrap, not a good choice for testing something you intend to keep.
Step 4: check the price against the metal
Purity and price are the same question from two directions. Once you know the karat and the weight, the metal value is arithmetic — and a quote that does not reconcile to it is telling you something.
At today's rate, Pakistan 22 carat gold is Rs 36,909.26 per gram. A 20 gram piece therefore contains Rs 738,185 of metal. Anything above that in the quote is making charges, wastage and tax — which should each be named separately.
- A quote well below metal value is not a bargain. Verify the karat before anything else.
- A quote far above metal value is not fraud — but the gap should be explained line by line, and you should be able to see the making charge as its own number.
- An all-in price with no breakdown cannot be compared against any other shop. Ask for the breakdown before comparing.