Few words in my trade cause more confusion than the ones we use to describe where a stone came from. Lab grown gemstones, synthetic, treated, simulated, created, enhanced. They get used loosely, sometimes carelessly, and occasionally on purpose to make a stone sound like something it isn't. After about twenty years at the bench and behind the loupe, I've decided the most useful thing I can offer isn't a sales pitch. It's a clear glossary.
So here is how a gemmologist actually uses these words, and why the distinctions matter when you're spending real money on something you intend to keep.
Natural: formed by geology, not by us
A natural gemstone is one that grew in the earth, by geological processes, over a span of time that makes a human lifetime look brief. An emerald is the green variety of the mineral beryl (Be3Al2Si6O18), coloured by traces of chromium or vanadium. Aquamarine, morganite and yellow beryl are the same mineral wearing different colours. Nature made all of them, and no two are identical.
Natural does not automatically mean untouched, which is where the next two words come in.
Synthetic: same stone, different birthplace
This is the term most often misunderstood. A synthetic gemstone is grown in a laboratory, but it has essentially the same chemistry, crystal structure and physical properties as its natural counterpart. Under the Italian UNI gemmological standards I trained against, these are classified as synthetic minerals, not fakes. A synthetic emerald is still beryl. A synthetic sapphire is still corundum. The recipe is the same; only the kitchen is different.
For emeralds there are two long-established methods. Flux-melt growth dissolves the ingredients in a molten flux and lets crystals form slowly. Hydrothermal growth uses hot, pressurised water to do something closer to what the earth does. Around 1960, Johann Lechleitner pioneered a hybrid: a thin hydrothermal layer of synthetic emerald grown over a natural beryl seed, sold under names like Emerita and Symerald. Clever work, and entirely legitimate, so long as the buyer is told.
This is also the honest answer to a question I'm asked constantly, usually phrased as "are lab grown diamonds real?" Yes. A lab grown diamond is real diamond, chemically and structurally identical to a mined one. The difference is origin and rarity, not authenticity.
Both are graded against the same criteria; our guide to the diamond 4Cs explains how that grading works. Every Lucano engagement ring is available with either a lab-grown or natural stone.
Imitation: looks like it, isn't it
An imitation, or simulant, is a different material that merely resembles the gem it's standing in for. Glass coloured green to pass as emerald. Cubic zirconia in place of diamond. A simulant has different chemistry, different structure and different properties. This is the crucial line: a synthetic emerald is an emerald grown in a lab, while an imitation emerald is not an emerald at all. Conflating the two is where a great deal of trade vagueness lives.
Treated: a real stone, improved
Treatment means a stone, natural or synthetic, has been modified to improve its appearance. Most of these processes are old, accepted and, in the right hands, stable. A few examples I work with directly:
- Heat treatment. Yellow beryl heated to roughly 400 to 450°C turns the soft blue of aquamarine, and that change is stable over time. Pink beryl, the variety sold as morganite, is heated more gently at 200 to 400°C to strengthen and stabilise its colour.
- Oiling and resin filling. Emeralds are naturally fractured stones. Around 90% of emeralds on the market are oiled to mask those fractures and improve clarity. It's why you should never clean an emerald with solvents, alcohol or ultrasonics, as you can strip the oil and leave the gaps exposed.
- Irradiation. Controlled radiation alters colour in certain stones, a standard process for some blues and other hues.
None of this is dishonest in itself. An oiled emerald is still a natural emerald. A heat-treated aquamarine is still aquamarine. Treatment is simply part of how the gem world has always worked.
So which words actually matter?
Here's the part the trade tends to skip. None of these categories is inherently good or bad. A beautifully grown synthetic sapphire can outperform a flawed natural one. A sensitively oiled emerald can be lovely and fairly priced. The problem has never been the existence of lab grown gemstones, synthetic gemstones or treated gemstones. The problem is non-disclosure: selling treated as untreated, synthetic as natural, or imitation as the real thing.
The jewellery industry runs on opacity. We don't. When you ask whether a stone is natural, synthetic or treated, I'll tell you plainly, every time, before you ask twice. That's the whole point of working with a gemmologist rather than a brochure.
If you'd like a stone explained in this kind of plain language before you commit to it, I'm always happy to talk you through exactly what you're looking at.
