How Are Lab-Grown Diamonds Made? What Engagement Ring Shoppers Should Know
How are lab grown diamonds made? A lab starts with a tiny slice of real diamond, called a seed, and grows new diamond crystal on it. It does this one of two ways: by recreating the intense heat and pressure found deep inside the Earth (HPHT), or by building the crystal layer by layer from carbon-rich gas (CVD). Either way, the finished stone is a real diamond, and many couples now choose one for their engagement ring.
This guide covers what lab-grown diamonds are, how CVD and HPHT compare, how they differ from moissanite and cubic zirconia, how gem labs identify and certify them, and what to look for when you choose a lab-grown diamond engagement ring.
What Are Lab-Grown Diamonds?
Lab-grown diamonds are diamonds made in a controlled lab instead of mined from the ground. They are pure carbon arranged in the same crystal structure as a mined diamond, so they have the same hardness, the same sparkle and the same durability.
What separates lab grown vs natural diamonds is origin, not what the stone is made of. A natural diamond formed over an enormous stretch of time underground. A lab-grown diamond is grown in weeks. Once either one is cut, polished and set in an engagement ring, it is still a diamond.
For a deeper look at that question, read our guide, Are Lab Grown Diamonds Real Diamonds?
Lab-Grown Diamond vs. Moissanite vs. Cubic Zirconia
Plenty of stones sparkle, but only some of them are diamonds. Cubic zirconia and moissanite are look-alikes, called simulants. A lab-grown diamond is not a look-alike. It is diamond.
Cubic zirconia (CZ) is a man-made crystal of zirconium dioxide. It looks bright when new, but it is softer than diamond and tends to scratch and turn cloudy with daily wear.
Moissanite is silicon carbide, a different gemstone entirely. It is doubly refractive, which splits light and throws off strong rainbow flashes. Next to a diamond, that fire looks different from a diamond's crisp white and colored sparkle.
Here is how the four compare:
| Property | Cubic Zirconia | Moissanite | Lab-Grown Diamond | Natural Diamond |
| What it is made of | Zirconium dioxide | Silicon carbide | Pure carbon | Pure carbon |
| Hardness (Mohs scale) | 8 to 8.5 | 9.25 | 10 | 10 |
| Refractive index | 2.15 to 2.18 | 2.65 to 2.69 | 2.42 | 2.42 |
| Dispersion (fire) | 0.058 to 0.066 | 0.104 | 0.044 | 0.044 |
| How it bends light | Singly refractive | Doubly refractive | Singly refractive | Singly refractive |
| Heat conductivity | Low | High | Very high | Very high |
The short version of lab grown diamond vs moissanite: if you want a diamond, moissanite is not one. The same goes for lab grown diamond vs cubic zirconia.
How Are Lab-Grown Diamonds Made? CVD vs. HPHT
There are two proven methods for growing gem-quality diamonds. Both start with a diamond seed. They differ in how they deliver the carbon that grows on it.
HPHT: High Pressure, High Temperature
An HPHT diamond is grown under conditions like those deep in the Earth's mantle.
- A small diamond seed goes into a growth cell with a very pure carbon source and a metal flux that melts during the process.
- A large press squeezes the cell to about 5 to 6 gigapascals of pressure while it is heated to roughly 1,300 to 1,600°C.
- The melted metal dissolves the carbon, which travels to the cooler seed and crystallizes on it, building a rough diamond.
CVD: Chemical Vapor Deposition
A CVD diamond is built from gas rather than squeezed into shape.
- A thin diamond seed plate is placed in a sealed chamber filled with methane and hydrogen.
- Microwave energy turns the gas into a glowing plasma at roughly 700 to 1,200°C, at low pressure.
- That energy frees carbon atoms from the methane. They settle on the seed and bond into diamond crystal, layer by layer, over several weeks.
So which is better, CVD vs HPHT? For an engagement ring, the method matters far less than the finished stone's cut, color and clarity. Many CVD diamonds are also heat-treated after growth to improve their color, which is permanent. A good grading report will tell you what you need to know about the stone in front of you.
A Short History of Lab-Grown Diamonds
Diamonds were first grown in labs in the 1950s. Those early stones were tiny and dark, and they went into cutting tools and abrasives, not jewelry. Gem-quality lab diamonds followed in the 1970s, but they were costly to make. Over the past few decades, better equipment and more precise growing methods made larger, clearer stones practical, and that is why lab-grown diamond engagement rings have become so popular.
Can a Jeweler Tell If a Diamond Is Lab-Grown?
Not by looking. Under a jeweler's loupe or a standard microscope, a lab-grown diamond shows the same facet reflections and brilliance as a mined diamond, and a handheld diamond tester reads both as diamond.
Telling them apart takes lab equipment. Gem labs such as the Gemological Institute of America (GIA) use tools like these:
- Spectroscopy: reads trace elements and tiny crystal defects. Most natural diamonds contain clusters of nitrogen, while CVD diamonds usually have almost none and can show other telltale signatures.
- Screening devices: desktop tools such as the GIA iD100 measure how a stone responds to light and flag lab-grown diamonds and simulants in seconds.
- Fluorescence imaging: under strong ultraviolet light, HPHT diamonds often show growth patterns that differ from those in natural diamonds.
Lab-Grown Diamond Certification: What the Report Tells You
A lab-grown diamond certification is a grading report from an independent gem lab. You will most often see IGI certified lab grown diamonds, and GIA grades lab-grown diamonds as well. Either way, the report grades the stone on the 4Cs: cut, color, clarity and carat weight.
Lab-grown diamonds are not automatically flawless. They can have inclusions and graining from the growing process, which is why the clarity grade still matters.
A solid report gives you:
- A laser inscription: the report number, and usually a note that the stone is lab-grown, is inscribed on the diamond's edge so the stone and paperwork can be matched.
- Online verification: you can look up the report number on the lab's website to confirm the details.
- The full picture: measurements, proportions, polish, symmetry and any treatment after growth.
Keep that report with your ring's other paperwork. It is useful if you ever need to insure or replace the stone. Our guide on how to insure a lab-grown diamond engagement ring explains why.
Choosing a Lab-Grown Diamond Engagement Ring
Choosing between natural and lab-grown comes down to your priorities, your style and your budget. At The Golden Gem, that choice is yours for the center stone and for every other gemstone on the ring.
Lab-grown diamonds typically cost much less than natural diamonds of the same size and quality. For many couples, that means a larger center stone, or more of the budget going toward the setting. If you are still working out a number, our engagement ring budget guide can help.
A few things matter more than the price tag:
- Cut quality: a well-cut diamond is the one that sparkles. See which diamond cut sparkles the most for help choosing a shape.
- Shape and setting together: an elongated oval, an emerald cut and a round brilliant each look best with different prong styles and band widths.
- Metal: choose 14K or 18K gold in white, yellow or rose, or platinum.
Lab-Grown Diamond FAQs
Are lab grown diamonds worth it?
For many couples, yes, as long as you are buying for beauty and meaning rather than resale. Lab-grown diamonds give you more size and quality for the money. They are not an investment, though. As production keeps getting more efficient, lab-grown prices have trended down over time, while natural diamonds have historically held their value more steadily.
Is heat treatment on a lab-grown diamond permanent?
Yes. Some CVD diamonds get an HPHT treatment after growth that removes a brownish tint. It changes the crystal itself, so the improved color will not fade or change over time.
Do lab-grown diamonds get cloudy or scratch easily?
No. A lab-grown diamond is a 10 on the Mohs scale, the same as a mined diamond, so it stands up to everyday wear. Like any diamond, it will look its best with regular cleaning.
See Lab-Grown Diamonds in Person
A diamond's sparkle is hard to judge on a screen. Whether you are shopping from Arvada or Lakewood, a visit to our Golden, CO showroom lets you compare lab-grown diamonds side by side with a Bridal Consultant. During your appointment the whole bridal showroom is yours, with no pressure and never rushed.
Visit The Golden Gem: 1111 Washington Ave, Suite 215, Golden, CO 80401. Call 720-761-5956.
