Lab grown or natural?

Are lab grown diamonds real diamonds?

Yes. The honest version of that answer is stronger than most sellers give you. Set a one carat lab grown stone next to a one carat natural stone of the same grade, under the same light. Nobody in the room can tell you which is which. Not us. Not a gemologist with thirty years behind a loupe.

They are the same mineral. Carbon in a cubic lattice, 10 on the Mohs hardness scale, refractive index 2.42 and the 0.044 dispersion that throws those flecks of colored light you can catch from across a table. Every property you notice while wearing a diamond is identical, because the two stones are the same substance.

A simulant is a different thing entirely. Cubic zirconia is zirconium dioxide and moissanite is silicon carbide. Both are softer, both bend and split light differently and both are obvious to anyone who handles stones every week. A lab grown diamond is not diamond-adjacent. It is diamond.

The Federal Trade Commission settled the wording in 2018, revising its jewelry guides to remove "natural" from the definition of a diamond. A seller cannot imply a lab grown stone is fake and cannot sell one without telling you what it is.

How a natural diamond forms

A natural diamond is old in a way that is difficult to hold in your head. Gem diamonds crystallized in the mantle, roughly a hundred miles beneath the surface. The ones being set into rings this year are between one and three and a half billion years old. They spent all of that time in the dark under pressure and then got a lift.

That lift is the part worth knowing about, because it is violent and quick. Kimberlite eruptions tore upward through the crust fast enough that the diamonds arrived intact instead of reverting to graphite on the way. Slow ascent gives you no diamonds at all.

The reason reversion is even on the table is the strangest fact in this whole subject. At the temperature and pressure of the room you are sitting in, graphite is the stable form of carbon and diamond is not. The stone on your hand is in the wrong state and is under no obligation to hurry about it. The rate of change is so slow that "eventually" stops carrying any useful meaning. Nothing about a lab grown stone changes this. Both are metastable. Both will outlast everyone reading the page.

How a lab grown diamond is grown

In weeks, by one of two routes, both of which start with a thin slice of diamond as a seed.

• HPHT, high pressure high temperature, reproduces mantle conditions around the seed and lets carbon crystallize onto it out of molten metal.
• CVD, chemical vapor deposition, builds the crystal a layer at a time inside a vacuum chamber, cracking a carbon rich gas into a plasma so carbon settles onto the seed plate.

Neither route is the better one and it is not a choice a buyer needs to make. The method appears on the grading report and has no bearing on how the finished stone looks in a setting.

How a gemologist separates them

Not by eye, not with a loupe and not with any of the standard tests, because the tests measure properties the two stones share. Separation comes down to reading how the crystal grew and what it picked up while growing, which needs laboratory instruments. Three tells do the work.

The first is growth structure. A natural crystal grew outward in octahedral layers over hundreds of millions of years. A CVD crystal grew as a stack of flat layers over about three weeks. Deep ultraviolet imaging shows that striped growth history directly. The stone carries a record of its own manufacture.

The second is nitrogen. Most natural diamonds contain nitrogen in their lattice, which puts them in the Type Ia classification. CVD stones are typically Type IIa, meaning nitrogen free, a category that also covers a small minority of natural diamonds and several of the famous historical ones. There is a pleasing irony in it. The laboratory stone is usually chemically purer than almost every diamond ever pulled out of the ground.

The third only applies to some HPHT material and it is our favorite. HPHT stones grow in molten metal and a few trap tiny iron and nickel inclusions from that flux. Those stones respond to a strong magnet. A diamond that a magnet can nudge has nothing wrong with it. It simply carries a bit of the machine still inside.

Why this page has no prices on it

A lab grown diamond costs a great deal less than a natural one at the same cut, color, clarity and carat. The gap has widened as growing capacity has increased. That is as precise as this page is willing to be, on purpose.

Every competing page quotes you a percentage. Lab grown wholesale prices have moved sharply and repeatedly, so those percentages were wrong within months of publication and are still sitting there being quoted. Ask for both numbers on the day you buy.

What Astra Jewelers does instead is set the two stones in front of you at matching specification with both prices attached. That comparison answers the question for your budget. A figure in an article answers it in the abstract, which is to say not at all.

Resale and insurance

Here is the difference that matters most. It is the one most comparisons rush past. Natural diamonds have an established secondary market. Lab grown diamonds largely do not. Because production capacity keeps expanding and unit costs keep falling, a lab grown stone bought today is unlikely to hold its price.

For a ring that is going to be worn for forty years, that may be irrelevant. For a purchase where part of the reasoning is holding value, it is the entire decision. Insurance follows replacement cost, so the lab grown stone is also cheaper to cover.

How to choose between them

Choose lab grown if you want the most size and the best grade your budget will carry on a piece that is bought to wear. Choose natural if the age and the origin of the stone are part of why you want it or if resale sits anywhere in your reasoning. Both are real diamonds. Neither choice is a compromise on how the finished ring looks on a hand.

We sell both and we have no reason to push either, which is a more comfortable position than it sounds. The interesting conversation is not which stone wins. It is what you want the ring to be. The answer to that is usually sitting in the first thing someone says when the tray comes out.

Astra Jewelers stocks and sources both at the studio in Upper Montclair. Come and look at them side by side with the certificates on the counter. We will walk you through the trade in front of the stones rather than over the phone.

What to check before you buy either

• Ask for the grading report and check the laboratory is one you can look up. GIA and IGI both grade lab grown stones.
• Find the report number laser inscribed on the girdle and ask to see it under magnification. It takes ten seconds and it ties the paper to the stone in your hand.
• Get it in writing that the stone is lab grown or natural. Disclosure is required, so vagueness on this point tells you what you need to know about the seller.
• Compare at the same four grades. A lab grown stone one color grade lower is a different stone, not a bargain.
• Ask what happens if you want to upgrade or reset the piece in ten years, which is where the resale difference stops being theoretical.

Common questions