Pearls
Judging a pearl without a certificate
Pearls have no grading report system the way diamonds do, so the buyer has to see for themselves. Lustre, surface, shape, and how to spot an imitation.
Pearls are unusual among gems in having no standardised certification system. The buyer has to judge for themselves more than with anything else in the case.
The good news is that the two criteria that matter most are visible to the naked eye, once you know what you are looking at.
Lustre is nearly everything
Lustre is how sharply a pearl returns light. A pearl with strong lustre reflects a window or a lamp as a defined shape, like a curved mirror. Not just a bright glow — an actual reflection.
The simplest test: hold the pearl at arm's length and look for your own reflection. If you can make out a shape, the lustre is good. If you see only a soft bright blur, the nacre is thin.
Thin nacre comes from short cultivation. Those pearls are much cheaper, and within a few years the nacre begins to peel and expose the bead underneath.
Surface, shape and size
A pearl is grown by an animal, so almost none are perfectly smooth. Minor surface marks are natural and cost little value if they fall where a drill hole or a setting hides them.
Perfectly round commands the highest price, followed by drop and oval. Baroque pearls, irregular by definition, cost far less — though many people prefer them precisely because no two are alike.
Size moves price steeply, because larger pearls take longer to grow and more of them fail. A 12 mm South Sea pearl can cost twice a 9-10 mm one of the same quality.
| Type | Typical size | Character |
|---|---|---|
| Freshwater | 6-9 mm | Affordable, wide colour range |
| Akoya | 6-8 mm | Sharpest lustre, very round |
| South Sea / Andaman | 9-15 mm | Large, deep satiny glow |
| Tahitian | 8-14 mm | Dark grey to peacock green |
Real or imitation
The classic test still works: rub the pearl gently against the edge of a front tooth. A real pearl feels slightly gritty because the surface is layered crystal. Glass or coated plastic feels perfectly smooth.
Also look at the drill hole. On a real pearl the edge is crisp and you can see nacre layers. Imitations often show flaking coating or a ragged rim.
Looking after them
Pearls are 2.5-4 on the Mohs scale — very soft — and nacre is an organic material that dissolves in acid.
The rule is simple: pearls go on last and come off first. Perfume, hairspray and cosmetics damage the surface permanently. After wearing, wipe with a barely damp soft cloth and let them air dry.
Store them separately from other jewellery, since metal and harder stones will scratch nacre. Do not seal them in an airtight plastic bag either — pearls need a little humidity or they craze.
Are cultured pearls real pearls
Yes. Natural pearls form by accident and are so rare they barely appear on the open market. Almost everything sold today is cultured, which is genuine nacre grown by a live oyster — a human simply starts the process.
How often should a pearl strand be restrung
With regular wear, every one to two years. Silk thread absorbs skin oils and perspiration and weakens. If you start to see gaps between pearls or the thread has gone grey, it is overdue.
Are golden pearls better than white
It is purely preference. Deep golden South Sea pearls are rarer and priced higher at the same size, but that does not make them higher quality. Judge lustre and surface first, whatever the colour.