--- title: "Lab-Grown Black Diamond Guide: How Black and Green Get Their Color" byline: "Love & Carat" series: colored_stones published: 2026-09-30T12:58:05.870Z updated: 2026-09-30T12:58:05.870Z canonical: https://loveandcaratnewyork.com/blog/lab-grown-black-diamond-green-diamond-color disclosure: editorial sources: - "Laboratory-Grown Diamond Services Details - https://www.gia.edu/gem-lab-service/laboratory-grown-diamond-grading-report-service" - "GIA to Use New Descriptive Terminology for Laboratory-Grown Diamonds - https://www.gia.edu/gia-news-press/new-descriptive-terminology-for-laboratory-grown-diamonds" - "How Diamond Treatments Can Impact Color, Clarity and Value of a Diamond | GIA 4Cs - https://4cs.gia.edu/en-us/diamond-treatments/" - "Black Diamond Buying Guide | GIA 4Cs - https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/" - "The Green Diamond: A Rare and Unique Gem | GIA 4Cs - https://4cs.gia.edu/en-us/blog/green-diamond/" --- # Lab-Grown Black Diamond Guide: How Black and Green Get Their Color _Written by Love & Carat about the stones we sell. Not an independent review._ **The short answer** - A colored lab-grown diamond gets its color either during growth or from a treatment afterward, such as annealing, high-pressure high-temperature (HPHT) processing or irradiation. - According to GIA, most black diamonds are treated, and green color in diamonds comes from radiation exposure; HPHT treatment can also turn brownish diamonds green. - According to GIA, its reports list known treatments, and it does not issue reports for coated diamonds, whose color can wear off. Check what a particular lab-grown diamond report says about its color rather than assuming it identifies when the color arose. - GIA says typically opaque black diamonds receive the single color grade Fancy Black and no traditional clarity grade. Don't pay extra for a clarity grade that isn't on the report. A lab-grown black diamond or lab-grown green diamond gets its color in one of two ways. Either the color forms while the stone grows, or it comes from a treatment afterward, such as annealing, high-pressure high-temperature (HPHT) processing or irradiation. Color may develop during growth or be changed afterward; coatings are another possibility, but GIA does not issue reports for coated diamonds. Check the report for what it actually establishes about color origin and known treatments, and ask if the cause is unclear. The rest of this guide covers how each color forms, how the reports word it, how these stones hold up in daily wear, and what to check before you pay. ## How does a lab-grown black diamond get its color? Lab-grown black diamonds are grown by [HPHT or chemical vapor deposition (CVD)](https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/), the same two methods used for colorless lab-grown stones. GIA describes them as similar to natural diamonds in chemical composition, crystal structure, hardness and brilliance. Our [glossary entry on lab-grown diamonds](/education/lab-grown-diamond) explains the growth side in more detail. The black itself is a different story from a natural black diamond. In natural stones, GIA explains, the dark look comes from [dense clouds of inclusions or graphitized fractures](https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/). In lab-grown diamonds, especially those turned black through treatment, GIA says the color comes from extremely high concentrations of crystal lattice defects that absorb light very strongly. Treatment is common with black diamonds of any origin. GIA describes annealing, a controlled heating and cooling process, as the usual route: > The process is very common for creating black diamonds. In fact, most black diamonds are treated. > (How Diamond Treatments Can Impact Color, Clarity and Value of a Diamond | GIA 4Cs) GIA also notes a second route: [irradiation can produce a green so deep](https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/) that the stone looks black. GIA adds that irradiated diamonds are not radioactive. You can see a difference, too. GIA says natural black diamonds tend to show more visual texture and depth, while lab-grown black diamonds have a flatter color and are often smoother, more uniform and glossier. If you want an even, inky black with a mirror-like surface, a lab-grown stone gives you that look for less. ## Where does the green in a lab-grown green diamond come from? [GIA describes radiation exposure as one cause of green color in diamonds](https://4cs.gia.edu/en-us/blog/green-diamond/); it also describes HPHT treatment as a way to turn some brownish diamonds green. In nature that radiation comes from uranium in rocks near the earth's surface. GIA lists a linear accelerator, gamma rays and a nuclear reactor as possible methods of artificial irradiation. There's a second route. GIA describes HPHT treatment, a form of annealing done in a press, as [often used to turn brownish diamonds into yellow or green](https://4cs.gia.edu/en-us/diamond-treatments/). The same kind of press can also grow diamond. Irradiation, GIA notes, can be followed by annealing to adjust the color further. Irradiation and HPHT treatment are both ways to produce green in diamonds; a lab-grown green diamond may instead have developed its color during growth. Ask what the report establishes about the particular stone. If the report does not establish the cause of color, ask for clarification before buying. Read what the report actually says about color origin and known treatments; don't infer a specific process it doesn't identify. Knowing a green diamond is lab-grown answers the question of the stone's origin, but not necessarily the cause of its color. With natural greens, GIA explains that because earth radiation is similar to laboratory radiation, [it isn't always possible for a lab to tell natural from treated color](https://4cs.gia.edu/en-us/blog/green-diamond/). A report can establish that a diamond is lab-grown, but that alone doesn't establish whether its green color developed during growth or was changed afterward. ## How does a grading report describe color and treatment? Every diamond we sell comes with a GIA or IGI grading report. Check the color description and any statements about color origin or known treatments; if the report doesn't answer your question, ask before buying. GIA lists a [Laboratory-Grown Colored Diamond Report](https://www.gia.edu/gem-lab-service/laboratory-grown-diamond-grading-report-service), a color identification version of it, and an add-on Diamond Color Treatment Letter. GIA says it laser-inscribes a lab-grown diamond's girdle with "Laboratory-Grown" and the GIA quality assessment number. On its treatments page, [GIA says its reports identify natural or treated color](https://4cs.gia.edu/en-us/diamond-treatments/); for a lab-grown diamond, read the particular report to see what it establishes about the color and any known treatment. It also says every GIA diamond grading report lists any known treatments, and that GIA laser-inscribes the girdles of diamonds it identifies as color-treated. Black diamonds are graded differently from colorless ones. According to GIA, black diamonds [fall outside the D-to-Z scale](https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/) and are evaluated under its colored diamond grading system. Typically opaque black diamonds do not receive traditional clarity grades. GIA says opaque black diamonds are assigned the single color grade "Fancy Black," rather than grades reflecting differences in tone or saturation. One more change to know about. On [June 2, 2025, GIA announced](https://www.gia.edu/gia-news-press/new-descriptive-terminology-for-laboratory-grown-diamonds) plans to use "premium" and "standard" quality descriptions for lab-grown diamonds instead of the natural-diamond color and clarity nomenclature; check the report and GIA's current services for the format in use. GIA said existing lab-grown reports remain valid. For the services it offers today, check [GIA's lab-grown services page](https://www.gia.edu/gem-lab-service/laboratory-grown-diamond-grading-report-service). Our [glossary entry on certificates](/education/certificate) covers how to read a report generally. **Read the origin line:** Look for any statement about color origin or treatment, and note exactly what the report does and does not establish. If a report you're shown doesn't make that clear, ask before you pay. ## Are colored lab-grown diamonds tough enough for every day? Yes, with a few sensible habits. GIA notes that diamonds rank [10 on the Mohs scale](https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/), and it describes lab-grown black diamonds as similar to natural ones in hardness. The same treatments that color these stones are, in GIA's words, stable: - **Annealing** and **HPHT** are stable treatments, and GIA grades diamonds treated these ways. - **Irradiation** is [stable to regular wear](https://4cs.gia.edu/en-us/diamond-treatments/), but GIA notes that irradiated diamonds may be more sensitive to the heat involved in repairs. - **Coating** is different. GIA describes it as an ultra-thin layer that can scratch, wear off and be damaged by heat or chemicals, and GIA won't issue a report for a coated diamond. That last point is the one to watch. A color that sits on the surface isn't one we'd put in a ring you wear every day. On setting: GIA says natural black diamonds, with their many inclusions and tiny cracks, [need to be set carefully](https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/) to avoid damage. It describes lab-grown black diamonds as more uniform, with an absence of visual flaws. We'd still pick a setting that covers the edges if your hands are busy, as we would for any center stone. **Tell your jeweler first:** If your stone's color comes from irradiation, mention it before any resizing or repair, since GIA notes these diamonds may be more sensitive to repair heat. Keep the report with the ring. ## Why are black diamonds cheaper, and what are they worth? A few things keep prices down, according to GIA: - **Treated black diamonds** are [more affordable than their natural-color counterparts](https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/). GIA notes they often start as heavily included gray or brown material. - **Natural black diamonds** are rarer, but GIA says lower demand keeps their prices more modest than top colorless stones. - **Lab-grown black diamonds** are often more affordable than mined ones, according to GIA, because they're produced more quickly in controlled conditions. Cheaper doesn't mean imitation. GIA separates lab-grown and natural black diamonds from [simulants such as moissanite, cubic zirconia, glass and synthetic spinel](https://4cs.gia.edu/en-us/blog/black-diamonds-what-you-need-to-know/), which only resemble black diamond and are less durable. For more on where lab-grown stones stand, see [our guide to whether lab-grown diamonds are diamonds](/blog/are-lab-grown-diamonds-real-diamonds). As for what a stone is worth: we don't appraise or value stones, and we won't promise resale value. Diamonds aren't investments, lab-grown or natural. Buy the one you love wearing. If you insure it, your insurer may ask for an independent appraisal. ## What should you check before you buy? Here's the short list we'd work through for any lab-grown black or green diamond: 1. **A grading report from GIA or IGI.** We only sell certified diamonds, and we'd never suggest skipping the report to save money. The report is the starting point; also check the stone's appearance and ask about anything the report does not establish. 2. **Lab-grown stated plainly.** The report should confirm it's a lab-grown diamond. For GIA, the girdle inscription says "Laboratory-Grown." 3. **Color origin and treatment.** Read any statements about color and known treatments; don't assume the report identifies exactly when or how the color developed. Ask for clarification if it doesn't answer your question. A disclosed treatment isn't necessarily a reason to rule out a stone. 4. **No coating.** GIA does not issue reports for coated diamonds, and a coating can wear off; ask about coatings even if you're shown a report. 5. **Read the grade actually shown.** GIA describes Fancy Black as its color grade for opaque black diamonds; check the wording on the particular lab-grown diamond's GIA or IGI report. If an opaque stone has no traditional clarity grade, don't pay extra for one that isn't there. 6. **Returns and shipping terms.** Our [returns policy](/policies/returns) is published in full, and every order ships insured and signed for. **Skip the clarity hunt:** GIA says typically opaque black diamonds do not receive traditional clarity grades and describes Fancy Black as a single color grade. Check the report in front of you before paying for a grade it doesn't show. Put the money into a shape you love and a size that suits the setting. Where to spend and where to save is simple here. If an evenly colored, deep black stone appeals to you, compare treated lab-grown black diamonds with disclosed, stable color and choose by appearance. If a natural-color and a treated lab-grown black diamond look the same to you, we'd choose the less expensive stone rather than pay for an origin you cannot see. We'd take the lab-grown stone and the saving. For green, compare the stones themselves as well as their reports; if two stones look the same to you and the treatment is disclosed, choose the less expensive one. **Choose the color you love, check the report for color origin and known treatments, and ask about anything it doesn't make clear; avoid coatings.** When you're ready to compare shapes, browse our [colored diamonds for engagement rings](/colored-diamonds) or start with [center stones](/) and build the ring around the one you choose. ## Frequently asked questions **How much is a lab-grown black diamond worth?** We don't appraise stones or put a value on them. Diamonds, lab-grown or natural, aren't investments, and nobody should promise you a resale price. If you insure the piece, your insurer may ask for an independent appraisal. **Is a lab-grown diamond a fake?** No. GIA describes lab-grown black diamonds as similar to natural diamonds in chemical composition, crystal structure, hardness and brilliance. Imitations are a different thing: they only look like diamond and are made from other materials. **Is a black diamond actually a diamond?** A black diamond can be natural or lab-grown; a dark imitation may look similar but is not a diamond. GIA lists moissanite, cubic zirconia, glass and synthetic spinel as possible simulants. Check the grading report to confirm the stone's identity. **Why are black diamonds so cheap?** According to GIA, treated black diamonds are more affordable than natural-color ones, natural black diamonds are held to modest prices by lower demand, and lab-grown black diamonds are often more affordable than mined ones. None of that makes a certified stone less of a diamond.