ethical and cost-effective options without compromising beauty. These diamonds are created using two primary growth methods: Chemical Vapor Deposition (CVD) and High Pressure High Temperature (HPHT). While some lab diamonds are sold untreated, many undergo post-growth treatments to enhance their appearance, addressing issues such as color inconsistencies and inclusions.
Understanding the differences between untreated and treated lab diamonds is essential when choosing the right stone. Each method has unique characteristics, benefits, and trade-offs, influencing factors like brilliance, structural integrity, and overall quality.
CVD Diamonds: Untreated vs. Treated
Untreated CVD Diamonds
CVD diamonds are grown layer by layer in a controlled environment, but this process can sometimes produce rough stones with visible imperfections:
- Brown Hue and Striation: Untreated CVD diamonds often exhibit a faint brownish tint and striations, or “anomalous birefringence,” due to interruptions in the growth process. These streaks resemble windshield wiper marks and are caused by stress in the crystal lattice.
- Lower-Quality Rough: Many CVD diamonds are grown using rough material that results in non-diamond carbon formations, affecting clarity and overall appearance.
- Type IIa Purity: Despite these issues, all CVD diamonds are guaranteed to be type IIa, meaning they lack detectable nitrogen or boron, which gives them a chemically pure structure. However, the presence of brown hues and striation can detract from their appeal.
Treated CVD Diamonds
To address these imperfections, most CVD diamonds undergo post-growth HPHT treatment, a process that uses high pressure and high temperature to:
- Remove Brown Hues: This treatment neutralizes the faint brown coloration, making the diamond appear more colorless.
- Improve Visual Appeal: By enhancing the diamond’s color grade, post-growth HPHT treatment makes CVD diamonds more marketable and visually appealing.
While treated CVD diamonds can look stunning after this process, it’s important to note that the treatment does not change the diamond’s inherent structural properties. For buyers, ensuring that the diamond has undergone proper certification and inspection is essential to avoid stones with hidden quality issues.
This 1.00-carat round lab-grown diamond from Brilliant Earth, created using the CVD growth method, displays a slight haze due to strain and striations in the carbon lattice, highlighting a common challenge with CVD diamonds.
Transparency is a crucial yet often overlooked factor in both natural and lab-grown diamonds. Imperfections in the carbon lattice, such as graining or deformation, can reduce transparency, resulting in a diamond with diminished sparkle. To avoid this, choose a vendor with a rigorous quality control process. Many budget vendors sell diamonds with significant transparency issues at lower prices. For the highest quality, I recommend Whiteflash, known for offering some of the best diamonds on the market. For more affordable options, James Allen provides reliable choices, and Blue Nile offers flexible payment plans.
HPHT Diamonds: Untreated vs. Treated
Untreated HPHT Diamonds
HPHT diamonds are grown using intense heat and pressure, replicating the natural diamond formation process. These diamonds naturally possess several unique characteristics:
- Perfect Crystal Structure: Unlike CVD diamonds, HPHT diamonds have no strain in their crystal lattice. This results in a flawless internal structure that many buyers find appealing.
- Boron and Blue Nuance: Boron is often used as a catalyst during growth, which can give HPHT diamonds a subtle blue hue, commonly referred to as “blue nuance.” While some people find this hue desirable, others may prefer a diamond without it.
- Metallic Inclusions: Metallic flux is used in the growth process, which can sometimes result in metallic inclusions. These inclusions can cause the diamond to be magnetic or electrically conductive, occasionally leading to misidentification as moissanite during testing.
- Type IIa and Type IIb Diamonds: HPHT diamonds can be either type IIa (nitrogen- and boron-free) or type IIb (boron present, nitrogen-free). Type IIb diamonds are rare and highly valued for their unique properties.
A 1.01 ct E IF Round Cut Precision Lab Grown Diamond from Whiteflash created using the HPHT method
Treated HPHT Diamonds
While most HPHT diamonds do not require post-growth treatments, they may still be treated to address specific issues:
- Reducing Blue Hue: In some cases, treatments are applied to minimize or remove blue nuance caused by boron.
- Enhancing Clarity: Visible metallic inclusions may be reduced or removed through certain post-growth processes to improve the diamond’s appearance.
Compared to CVD diamonds, treatments are less common for HPHT diamonds due to their naturally superior crystal structure and consistent growth process. However, it is still essential to confirm whether a diamond has been treated, as untreated HPHT diamonds are often more structurally perfect.
Comparison: Choosing Between CVD and HPHT Diamonds
When deciding between untreated and treated lab diamonds, it’s important to weigh the trade-offs associated with each growth method. Here’s a side-by-side comparison:
Feature | CVD Diamonds | HPHT Diamonds |
Untreated Characteristics | Brown hue, striation, and crystal strain | Perfect crystal structure, possible blue nuance |
Post-Treatment Goals | Removes brown hues, improves color | Reduces blue hue, enhances clarity |
Crystal Structure | Strain present in untreated diamonds | Strain-free, flawless lattice structure |
Magnetic/Electrical Properties | None | Possible due to metallic inclusions |
Preferred Type | Type IIa post-treatment | Type IIa or Type IIb untreated |
CVD Diamonds: Treated CVD diamonds can be a more affordable option with excellent visual appeal. However, untreated CVD diamonds may exhibit imperfections that detract from their quality.
HPHT Diamonds: Untreated HPHT diamonds are structurally superior, with no strain and a more consistent crystal lattice. They are ideal for those prioritizing perfection, but buyers should be mindful of potential blue nuances or metallic inclusions.
Conclusion
Choosing between untreated and treated lab diamonds ultimately comes down to understanding the unique characteristics and trade-offs associated with CVD and HPHT diamonds.
Treated CVD diamonds can offer excellent visual appeal by addressing issues such as brown hues and striation, but untreated CVD diamonds may exhibit imperfections that affect their quality. Meanwhile, HPHT diamonds are naturally more structurally perfect, with no strain in the crystal lattice. However, buyers should be aware of potential blue nuance or metallic inclusions, which may appeal to some but not others.
When selecting a lab diamond, prioritize certifications like those from GIA or GCAL and request detailed images or videos to inspect the stone’s clarity and color. Whether you choose a treated CVD diamond for its affordability or an untreated HPHT diamond for its structural integrity, understanding the growth methods and treatment processes will help you make an informed decision that aligns with your preferences and budget.
By considering these factors, you can confidently select a lab diamond that combines beauty, quality, and value, ensuring it shines for years to come.
