A large share of the "copper" jewelry sold online isn't solid copper. It's brass, zinc alloy or steel with a thin copper-coloured layer on top — often thinner than a sheet of paper.
Sellers rarely lie outright. They just say "copper" and let you assume. The listing photographs identically either way, and the difference only shows up months later when the plating wears through at the contact points and a different metal appears underneath.
Here are seven ways to check, ordered from most to least reliable, with honest notes on which ones don't work as well as the internet claims.
1. Look at the colour — properly
This is the most useful test and most people do it wrong, because they look at one piece in isolation. Colour only reads accurately in comparison.
- Pure copper is reddish-orange. Salmon or rose-toned. In daylight it looks warm and slightly pink.
- Brass is yellow-gold. Noticeably more yellow, with no pink in it.
- Bronze is browner and duller than both.
Put the piece next to a copper coin or a length of household copper pipe in daylight. Side by side, the difference is obvious in a way it never is alone. Indoor lighting — especially warm bulbs — will fool you, so use a window.
2. Check the wear points
The most reliable test on a piece you already own, and it costs nothing.
Plating wears through where the piece rubs most: the inner surface, the edges, the underside of a cuff where it sits against the wrist bone. Look closely at those areas in good light. If you see a yellowish or silvery metal showing through a copper-coloured surface, you have plated base metal.
Solid copper has no "underneath." It wears to more copper.
3. Watch how it ages
Solid, uncoated copper tarnishes and patinas evenly, all over. The whole piece deepens together, darkest in the recesses where your skin doesn't rub it.
Plated pieces behave differently. They stay bright for months — the plating is often lacquered too — and then go patchy, with worn areas darkening while sealed areas stay shiny. Uneven, blotchy ageing is a plating signature.
Related: bare copper marking your skin green is a reasonable sign there's no coating between metal and skin. Not proof of purity, since brass and bronze also react — but a sealed or plated piece usually won't mark at all.
4. The magnet test — useful, but not for what people think
You'll read everywhere that "copper isn't magnetic, so if a magnet sticks it's fake." That's half right, and the half that's missing matters.
Copper is not attracted to magnets. Neither is brass. Neither is zinc alloy. So a magnet not sticking tells you only that there's no steel or iron in the piece — it does not distinguish copper from brass, which is the substitution that actually happens most.
What a magnet does rule out is steel-cored plated jewelry, which is common at the cheapest end. If a magnet grabs it firmly, it's plated steel and the question is settled.
There's a more interesting version. Copper is diamagnetic, so a strong neodymium magnet slid down a thick piece of solid copper falls noticeably slowly, dragged by induced eddy currents. It's a real effect, but a bracelet is usually too thin for it to show clearly, so treat it as a curiosity rather than a test.
5. Weigh it
Copper is dense — about 8.96 grams per cubic centimetre. The common substitutes sit lower: brass is roughly 8.4 to 8.7, zinc alloy considerably lower, aluminium only 2.7.
You won't measure density at home without displacement equipment, but you can use the crude version: solid copper feels heavier than it looks. A cuff that feels light and hollow for its size is a warning sign. Aluminium-cored pieces in particular feel obviously, almost comically light once you've held a solid one.
The brass–copper gap is too small to feel, so this test catches cheap alloys, not brass.
6. The scratch test
Conclusive, and mildly destructive — so do it somewhere invisible, like the inner surface at the very end of a cuff.
Scratch firmly with a needle or the corner of a file. Plating is thin; a determined scratch goes through it and reveals the base metal, which will be a visibly different colour. Solid copper shows fresh, bright copper in the scratch — the same metal, just cleaner.
Keep it small. A fresh scratch will darken back to match within a few weeks of wear.
7. Price and stamps
Copper is a commodity with a public price. A solid copper cuff of any real weight can't be made and shipped for a few dollars, so a very low price is itself information.
Look for a stamp too — Cu, copper, or a purity figure like 99.9%. A stamp isn't proof, since anyone can stamp anything, but reputable makers usually mark their work and anonymous plated stock usually doesn't.
Tests that don't work as well as claimed
The sound test
The theory is that brass rings brightly and copper gives a duller thud. It's true of large objects like bowls and bells. On something as small and thin as a bracelet the difference is too slight to judge, and shape affects it more than material does. Ignore this one.
The vinegar test
Copper reacts with vinegar and brightens. So does brass. It confirms you have some reactive bare metal rather than a lacquered or plated surface, which is mildly useful, but it doesn't identify which metal.
"It turned my finger green, so it's real"
Brass and bronze also mark skin. This tells you the surface is bare, not what it's made of.
Does it actually matter?
Depends what you want from the piece.
If you want something copper-coloured for a season, plated is fine and cheaper. It won't mark your skin while the coating lasts.
It matters if you want a piece that lasts and ages. Plating wears through — always, eventually — and once it does the piece is finished, because you can't polish a bracelet back to a metal that was never underneath. Solid copper has no failure mode of that kind. Polish it and it's bright again; leave it and it deepens. Twenty years in, it's still copper all the way through.
It also matters if you've reacted to jewelry before. Plated pieces have base metals underneath that can include nickel, which is a far more common cause of contact allergy than copper. Once the plating wears, that base metal is against your skin.
What we make
Every Healing Monk cuff is solid copper — unplated, uncoated, hand-forged in Nepal. There's no base metal, no lacquer and no plating to wear through, which is why ours tarnish, patina and sometimes mark skin. Those are all the same property, and it's the property you're buying.