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How to tell if a gold nugget is real

Natural gold nuggets have tell-tale signs that a fake cannot copy. These are the checks you can do at home and what you should ask the seller for before you buy.

1. Look at the surface with a magnifier

A natural nugget is irregular all over. It has small hollows, relief rounded by water and, sometimes, traces of quartz or soil in the cavities. The colour is a warm, even yellow, with brighter areas where the river has polished it.

Be wary if you see mould marks, edges that are too clean, perfectly round bubbles or an identical shine across the whole piece: these are typical of gold that has been melted and cast to imitate a nugget.

2. Rule out pyrite, “fool’s gold”

Pyrite is the most common mistake. It is easy to tell apart:

• Shape: pyrite forms crystals with flat faces and right angles; gold never does.
• Colour: pyrite is paler and more brassy, with greenish tints.
• Hardness: pyrite is hard and brittle. Gold is soft: a needle will mark it, and if you strike it, it bends without breaking.
• Streak: on unglazed porcelain, pyrite leaves a greenish-black streak; gold leaves a golden-yellow one.

3. Check the density

Gold is one of the densest metals there is, about 19 times denser than water. A nugget feels surprisingly heavy for its size. With a precision scale and a glass of water you can work out its density: weigh the piece dry, then hang it from a thread in the water and note how much weight it “loses”. Divide the dry weight by that difference: a natural nugget with its natural silver content gives a high value, usually between 15 and 19. Brass or plated imitations come out far lower.

For very small nuggets, under 0.5 g, this test needs a 0.001 g scale to be reliable.

4. Use a magnet

Gold is not magnetic. If the piece sticks to a magnet, it is not gold or it has iron inside. Not sticking does not prove it is gold, but sticking rules it out.

5. Ask the seller for documentation

A serious seller states the exact weight, the origin of the piece and sharp photos of every side. At Gold Nuggets Minerals each nugget is weighed and photographed in macro. And when you buy on Catawiki, your payment is held until you receive the piece.

Summary

• Irregular, rounded shape with no flat faces or mould marks.
• Soft, non-magnetic and very heavy for its size.
• Weight, origin and photos documented by the seller.