How to identify a piece's base metal (practical tests)
A client walks in with an old piece in her hand and asks: "what is this made of?" In the old days, I saw resellers freeze. Not anymore. You will leave this lesson with five tests you can run at the counter, no lab, in under two minutes. They do not replace a technical report — that is what the factory exists for, with microscopy and XRF — but they give you the repertoire to answer with confidence and still highlight what you sell.
Lesson 1 of this module taught you what brass is. Lesson 2 covered hypoallergenic. Lesson 3 covered steel, sterling silver and bronze. This lesson is the stitching: how to look, hold, and listen to a piece to form a solid hypothesis.
Test 1: weight in the hand
The most immediate difference between a brass piece (good demi-fine) and a zamac one (cheap costume jewelry) is weight. Brass is dense: solid, present, feels like "something". Zamac is light, hollow to the touch, gives the impression of painted plastic. Place a Herreira piece in the center of your palm and let it drop a few centimeters into the other hand — the short, firm impact of brass is different from the empty impact of zamac.
This test alone resolves ninety percent of doubts between real demi-fine and costume jewelry.
Test 2: exposed color
Look for an area where the plating may have worn off: inside a ring, behind a hoop, on a clasp, on a friction point. If an amber-yellow color shows up underneath, the base is probably brass. If it is silver-gray, it could be surgical steel or nickel. If it is brown-greenish, suspect bronze.
No wear anywhere? Good news: the plating is intact. Use the other tests to hypothesize the base.
Test 3: sound
Take two similar pieces (two rings, two pendants) and tap them gently against each other, near your ear. Brass has a short, full metallic sound. Zamac has a muted, low sound with no resonance. Solid sterling silver has a high, clear, almost bell-like ring. Surgical steel has a sharp, metallic sound but a different timbre from brass — "harder".
It is a subjective test that trains the ear over time. But for those who work with demi-fine daily, it becomes a tool.
Test 4: magnet reaction
This one is definitive for ruling out steel. Take a common magnet (a fridge magnet works for the amateur version; a neodymium magnet works better) and bring it close to the piece. Brass does not attract. Bronze does not. Sterling silver does not. Copper does not. Steel does — it attracts.
If the piece sticks to the magnet, it is steel (surgical or common). If it does not stick, you have ruled out steel and the game is between brass, bronze, sterling silver, copper. Use the other tests to refine.
Test 5: internal marking
Solid jewelry usually has a stamp. For sterling silver, look for "925", "Ag 925" or "sterling". For solid gold: "750" (which is 18k), "585" (14k), "375" (9k). In demi-fine, there is usually no karat stamp — what you may find is the manufacturer's logo or a line marking.
The absence of "925" or "750" does not condemn the piece — it just confirms it is not solid jewelry. It could be quality Herreira demi-fine, or it could be cheap costume. The other four tests sort that out.
Reading everything together
You rarely use a single test alone. The method is to combine:
- Good weight + exposed amber-yellow + no magnet pull = plated brass, likely quality demi-fine.
- Good weight + gray color + magnet pull = surgical steel, usually unplated.
- Good weight + silver shine + no magnet + "925" stamp = solid sterling silver, jewelry.
- Low weight + muted sound + odd exposed color = costume jewelry.
When in doubt, ask the factory for help. Herreira runs XRF analysis on pieces you want to confirm — that is one of the services you access as a reseller. Module 4, on factory quality control, will detail how that process works.
The pocket phrase
"To identify a base, I look at four things: weight, color where the plating wore off, magnet reaction, and internal stamp. In twenty seconds I know whether it is brass, steel, sterling silver or costume — and I can explain why."
What to practice this week
Gather five pieces from different origins: two Herreira, one jewelry piece (sterling silver or gold), one costume, one piece you cannot identify. Apply the five tests to each one and write the result in two lines. A week from now you will be doing this from memory, and your technical authority will be visible in every interaction.