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Do Lab Grown Diamonds Pass a Diamond Tester? What You Need to Know

Many buyers wonder whether a lab grown diamond can truly be identified as “real” using standard tools. As lab grown diamond options become more popular, this question matters more than ever—especially for those comparing them with natural diamonds in terms of authenticity and performance.

round cut lab diamond engagement ring

Table of Contents

What Is a Diamond Tester and How Does It Work?

A diamond tester is a handheld device designed to identify diamonds based on their physical properties. Most commonly, testers measure thermal conductivity, which refers to how quickly heat passes through a material.

Diamonds—whether natural or lab grown—conduct heat extremely well. When the tester detects this high level of conductivity, it typically signals that the stone is a diamond.

Some advanced testers also measure electrical conductivity, which helps distinguish between diamonds and certain simulants like moissanite.

Do Lab Grown Diamonds Pass a Diamond Tester?

Yes, lab grown diamonds do pass a diamond tester. This is because they share the exact same physical, chemical, and optical properties as natural diamonds.

When tested with a standard thermal diamond tester, a lab grown diamond will register as a real diamond. The device cannot differentiate between lab grown and mined diamonds because both conduct heat in the same way.

This is a key point: diamond testers confirm material, not origin.

Why Diamond Testers Cannot Tell the Difference

The limitation comes down to what the tester is actually measuring. Since both lab grown and natural diamonds are made of pure carbon arranged in the same crystal structure, their thermal and electrical behavior is nearly identical.

As a result, standard testers are not designed to identify whether a diamond was formed underground or created in a lab. They simply confirm that the stone is indeed a diamond.

Can Any Tester Distinguish Lab Grown from Natural Diamonds?

Only specialized equipment can reliably tell the difference. These tools are typically used by professional gemological laboratories.

Advanced methods include:

Spectroscopy analysis
Examines how the diamond interacts with light at a microscopic level.

Growth pattern detection
Identifies structural differences formed during lab creation.

Fluorescence imaging
Reveals patterns that are unique to lab grown diamonds.

These tests require controlled environments and are not available in standard retail settings.

Lab Grown Diamonds vs Diamond Simulants

It is important to distinguish lab grown diamonds from simulants such as cubic zirconia or moissanite.

Lab grown diamonds
Made of carbon with the same crystal structure as natural diamonds.

Moissanite
Made of silicon carbide, with different thermal and electrical properties.

Cubic zirconia
A synthetic material that does not share the same hardness or conductivity.

A diamond tester will typically identify moissanite differently if it includes electrical conductivity detection, while cubic zirconia will not pass as a diamond.

Are Lab Grown Diamonds “Real” Diamonds?

Yes, lab grown diamonds are real diamonds. They are not imitations or substitutes. The only difference lies in how they are created.

Natural diamonds form over billions of years under the Earth’s surface. Lab grown diamonds are produced using advanced methods such as HPHT or CVD in a controlled environment.

In both cases, the end result is the same material with the same durability, hardness, and brilliance.

pear cut lab diamond cluster engagement ring

Pear Cut Lab Diamond Cluster Ring

marquise cut lab diamond nature inspired engagement ring

Marquise Cut Diamond Ring

round cut lab diamond cluster nature inspired engagement ring

Round Diamond Ring Set

emerald cut lab diamond cluster ring

Emerald Cut Lab Diamond Ring

Why This Matters for Buyers

Understanding how diamond testers work helps buyers make informed decisions. If a lab grown diamond passes a tester, it confirms that the stone is genuine—not a fake or simulant.

This reassurance is particularly important when purchasing engagement rings or fine jewelry, where authenticity and long-term value are key considerations.

It also highlights why certification and trusted sourcing matter more than simple at-home testing.

Why Choose MollyJewelryUS for Lab Grown Diamond Jewelry

Choosing where to buy your diamond is just as important as understanding what you are buying. MollyJewelryUS focuses on lab grown diamond jewelry that combines quality, design, and flexibility.

Each piece is crafted with attention to detail, ensuring the diamond performs well visually and structurally. More importantly, MollyJewelryUS supports full customization. Buyers can choose the diamond shape, size, setting style, and metal type to create a ring that fits their exact preferences.

This approach allows for more control over both design and budget. Instead of selecting from limited options, customers can create something that feels personal while still benefiting from the value of lab grown diamonds.

For those looking for engagement rings or custom jewelry, this level of flexibility makes a meaningful difference.

Common Myths About Diamond Testers and Lab Diamonds

Lab diamonds will fail a diamond tester
This is incorrect. Lab diamonds pass standard diamond testers just like natural diamonds.

Diamond testers can identify origin
False. Testers only detect material properties, not how the diamond was formed.

Lab diamonds are the same as fake diamonds
Incorrect. Lab diamonds are real diamonds, while simulants are different materials.

Clearing these misconceptions helps buyers better understand what they are purchasing.

Conclusion

Lab grown diamonds do pass diamond testers because they are real diamonds with identical physical properties to natural ones. While testers confirm authenticity, they cannot distinguish origin.

For buyers, this means lab grown diamonds offer the same performance, durability, and brilliance as mined diamonds, with added flexibility in price and design. Understanding how testing works removes uncertainty and helps you choose with confidence.

FAQs About Lab Grown Diamonds and Diamond Testers

Do lab grown diamonds pass a diamond tester every time

Yes, lab grown diamonds pass standard diamond testers because they share the same thermal conductivity as natural diamonds.

No, a diamond tester cannot determine whether a diamond is lab grown or natural, as it only measures physical properties.

Some basic testers may misidentify moissanite, but advanced testers that measure electrical conductivity can distinguish it from diamonds.

Yes, lab grown diamonds are real diamonds with the same chemical and physical properties as natural diamonds.

Introduction

From an environmental sustainability perspective, all of our items are made to order. This production approach allows us to minimize raw material waste, avoid overproduction, and ensure that each piece is crafted specifically for the customer in optimal condition.

Please note that production typically takes approximately 2–3 weeks. As each item is individually made with care and attention to detail, we believe the additional time ensures a higher level of quality and craftsmanship.

  • Delivery time = production time + shipping time
  • We mostly use USPS as our partner for domestic shipping.
  • We select different shipping carriers for international orders based on the specific circumstances of each country.
  • A tracking number will be updated after we send out the package.

Production Time

Please allow an additional 4 business days for Silver and Platinum pieces. Weekends and public holidays are not counted as business days.

  • General production time: 21 business days.
  • Expedited production time: 14/18 business days.

Shipping time

  • Domestic (United States): Delivery 3-5 business days after production finishes.
  • Other Regions: Delivery 5-10 business days after production finishes.
  • Note: Couriers may not deliver on weekends. International shipments can sometimes experience delays in customs clearance.

Shipping Fee

  • Domestic (United States): Free shipping.
  • Other Regions: From USD$40 to USD$100. You may use the shipping calculator on the cart page to view specific costs.
  • Note: If the shipping address is not accessible, we will contact you before production.

About Customs Duties

  • Duty-Free Coverage: We cover customs duties for packages sent to Canada, Australia, and the United Kingdom, where we have partner warehouses.
  • Disclaimer On Customs Duties: For other regions, all customs and import duties would be charged once the package(s) arrive in the destination country. These charges, if any, must be paid by the customers. If the customers refuse to accept the package due to import duties or taxes, they will assume full responsibility for all return shipping, customs fees, and handling charges.

Need Help?

Custom Wedding Band Options
Made to Match Your Engagement Ring

Finding a wedding band that truly fits your engagement ring can be challenging. With our Custom Fit Service, any curved wedding band, enhancer wedding band, or open wedding band can be tailored to match your ring’s exact shape — even if your engagement ring was not purchased from us. In this guide, we’ll walk you through our services and processes in detail. Let’s get started!

Why do you need a custom wedding band?

More and more couples are choosing unique, personalized engagement rings, making flexible customization options especially important when finding the right wedding band. Ready-made bands are designed with general curves and do not account for the specific height, stone shape, prong placement, or profile of your engagement ring.

When the band does not match the engagement ring, you may experience:

* Visible gaps between the two rings

* Rubbing or collisions that can loosen stones over time

* Instability, causing the rings to twist or catch on clothing

* A mismatched appearance that does not look intentional

To solve these problems, our custom-fit wedding bands eliminate them by tailoring to the exact structure of your engagement ring, ensuring a seamless fit, comfortable wear, and a cohesive look from every angle.

Case Study 1: Customizing the Curvature of a Curved Wedding Band

In this example, the engagement ring features an organic, asymmetrical cluster design, a structure that most ready-made curved bands cannot naturally follow.

The first image clearly shows this issue: the unmatched curvature leaves a gap in the left side and causes the two rings to sit separately rather than as a cohesive set.

After applying our Custom Fit Service, the wedding band’s curve was redesigned to mirror the exact outline of the engagement ring. The result is a customized curvature that fits snugly, creating a unified, intentional look from every angle.

Case Study 2: Customizing the Gap of a Open Wedding Band

In this example, the customer selected an open wedding band to pair with a halo engagement ring. However, the original opening gap of 7.8mm was too wide for the engagement ring’s setting. This caused the two sides of the open band to sit too far apart, preventing the band from framing the center stone in a balanced, intentional way. To achieve a perfect fit, we reduced the gap from 7.8mm to 5.7mm. By customizing it, the open band now aligns seamlessly with the engagement ring’s profile and is nestled naturally around the halo setting.

Case Study 3: Customizing the Inner Spacing & Curvature of a Ring Enhancer

In this example, the customer chose a ring enhancer to frame an engagement ring with unique center setting and shank. However, the original enhancer was designed with general proportions: the inner spacing was too narrow, and the curvature did not match the engagement ring’s profile. As a result, the engagement ring could not slide in naturally, and the curvature is not the perfect one.

To create a perfect pairing, we adjusted two key elements:

1) Inner Spacing Adjustment: the gap between the two bands of the enhancer was widened so that the customer’s engagement ring could fit comfortably inside without friction or pressure on the prongs. This ensures the rings stack smoothly and remain stable during daily wear.

2) Curvature Refinement: we reshaped the curves to echo the exact outline of the engagement ring’s halo and basket. This prevents unwanted gaps and allows the enhancer to hug the ring in a balanced, symmetrical way.

How Our Custom Fit Service Works?

We make the custom-fit process easy and stress-free. Simply share photos and measurements, and we will customize a wedding band that matches your engagement ring beautifully — yes, without sending it in! Here’s how:

1) Share Photos and Measurements: To begin, we ask for clear photos of your engagement ring along with three specific views (front, side, and top).
We also need a few basic measurements such as: *Length & Width of the Center Stone, *Setting Height, *Band Width & Thickness

2) We Create a CAD Model of Your Engagement Ring: Using your photos and measurements, our designers build a precise digital model of your engagement ring. This allows us to see its curvature, profile, height, and overall structure accurately.

3) We Tailor the Wedding Band for a Perfect Fit: Based on the style you choose, whether it is a curved wedding band, open wedding band, or ring enhancer, we adjust every detail to match your engagement ring. This may include: 1️⃣ Refining the curvature to match your ring’s outline. 2️⃣ Adjusting the opening distance for open bands. 3️⃣ Modifying the inner spacing of enhancers to fit around the setting. 4️⃣ Matching band width or thickness when requested (extra cost might be required).

4) Modification Confirmation: We will share the customized design with you for confirmation. Once approved, we begin crafting your one-of-a-kind wedding band.

Our goal is to ensure your wedding band does more than sit beside your engagement ring — it should complement it flawlessly, as if it were made for your story from the beginning.

Frequently Asked Questions

Do I need to send in my engagement ring for the custom fit process?

No, you do not need to ship your ring to us. We can create a perfectly fitted wedding band using photos, three specific views, and a few simple measurements.

Yes. Our Custom Fit Service allows us to tailor any wedding band to match your engagement ring’s unique shape, height, and setting—whether it’s a solitaire, halo, cluster, three-stone, unique design, or a custom ring that is not purchased from us. We tweak all the details to ensure you get a perfect wedding set.

The initial modeling stage takes 1–3 days, during which we create a digital representation of your engagement ring and customize the band design. Once you approve the design, production typically takes 2–3 weeks, the same as you selected on the product page.

Yes. Our Custom Fit Service works for any engagement ring, regardless of where it was purchased.

Depending on the design you choose, we may adjust:

  • The curvature of the band

  • The opening distance of an open band

  • The inner spacing of a ring enhancer

  • The band width or thickness (extra cost might be required if needed)

Absolutely. We will send you a detailed digital mock-up showing how your curved band aligns with your engagement ring. Production only begins after you approve the design.

The service is $100, available as an add-on option on our wedding band product pages.

This is extremely rare due to the precision of our modeling process, but if an issue arises, please be confident that we stand behind our work. Rest assured that we will review the details and offer a solution based on the specific situation.

Yes. In many cases, a straight band can be reshaped with a custom curvature to match your engagement ring. Feel free to contact us if you have any customization ideas.

Yes, we can. In addition to our Custom Fit Service, which tailors a wedding band specifically to your engagement ring, we can create custom wedding band designs that are not listed on our site. Feel free to contact us if you are interested in working with us for something special!

Yes. We can customize men’s wedding rings to complement women’s engagement rings or wedding bands. Whether you want both rings to share matching silhouettes, profiles, design elements, or finishes, we can tailor the men’s band to create a coordinated and cohesive set that feels connected while still reflecting each person’s style.

1. Getting Started:

Online shopping offers a wide variety of choices, but when it comes to purchasing rings, it can be tricky—you can’t be certain of the fit without trying it on!

At MollyJewelryUS, we completely understand your concerns, which is why we’ve created this guide to make your decision easier.

Please take the time to carefully review this guide, as all of our rings are made to order, and a 35% restocking fee applies to exchanges and refunds.

Now, let’s walk you through the measurement process!

2. Key Points to Know About Ring Sizes:

1) Different Bandwidth Affects The Wearing Experience

  • The Bandwidth We Commonly Use: We usually use a 1.4 to 2mm bandwidth for our women’s rings, which can be considered Narrow Bands. Please check the specific bandwidth in the product description section.
  • Narrow Bands May Feel Larger: For rings with a narrower width, some customers may find that the sizes feel larger than expected. This is because narrow bands apply less pressure on the finger, making them feel looser when worn.
  • Wider Bands and Enhancer Bands May Feel Snugger: A ring with a wide band usually feels tighter than its actual size because it covers a larger area of the finger. Therefore, if you choose a wider ring (bigger than 2mm) or enhancer band (also known as a ring guard or ring jacket), then you may need to choose a quarter or half size larger than the narrower ring to ensure comfort.
  • Adjusting for a Perfect Fit: Please know the bandwidth affecting the wearing experience before your purchase to ensure that you get the right size.

2) Resizing Considerations

  • Resizing Limitations: Not all rings can be resized easily. Rings with intricate designs, and eternity bands with stones all around may have limited resizing options. It’s important to choose the correct size from the start if you’re considering these styles.
  • Potential Risks of Resizing: Resizing can sometimes weaken the structural integrity of a ring, especially if it’s adjusted significantly. For rings with side stones, resizing can also affect the setting of the stones and can cause them to fall out easily.
  • Alternatives to Resizing: If resizing isn’t an option, there are alternatives like using sizing beads, ring guards, or exchanging the ring for the correct size if possible. These solutions can help achieve a better fit without compromising the ring’s design or structure.

3. How To Determine Ring Size?

1) Measure A existing rings

* If you know there is a ring that fits perfectly, but you are not sure about its size: Measure the inside diameter and the bandwidth by placing a ruler either on top of the ring or underneath it.

* Please send us some photos according to the following pictures, and we will assist you in choosing the correct size!

2) Use a ring size gauge to find out the perfect size

* If you don’t know the size at all, this would be the best way to take your measurements! Since it’s metallic, it more closely resembles the feeling of wearing a ring, and you can easily tell the size by checking the labels. If you want to be foolproof, you can also take a photo according to Method 1, and send it to us.

3) Use a ring sizer for the measurement

* Please don’t snap it too tightly or loosely, make sure it can turn around on your finger, but there are no gaps. Sending us a picture of wearing it on your finger would be helpful for the judgment.

4) Get sizing at your local jeweler

It’s a good idea to get sized at a nearby jeweler! However, please ask them about the bandwidth they usually use. Just like mentioned at the beginning, a ring with a narrow band will fit slightly larger on the same size, while a ring with a wider band will fit more snugly. The reasoning is simple: the more metal on your finger, the more space it takes up and the tighter it will fit.

5) Measure the circumference of The finger

Unlike metal or plastic, paper strips and thread are thicker and more flexible. As a result, they can create a slight bulge or slack when wrapped around the finger, leading to a measurement slightly larger than the actual size.

Though this way is simple and convenient, it is usually used as a secondary insight, as it may not provide the same accuracy as professional ring sizing tools.

Notice: Please measure multiple times to ensure errors are minimized. Additionally, please let us know your/her height and weight as a reference if you intend to use this method.

*Use a strip of paper, a piece of string, or a measuring tape around your finger and mark the overlap. Then, take it off, make it straight, and measure from the beginning to the overlap.

Please send us a photo of the measuring strip or string.

*Use a strip of paper or a piece of string around your finger and mark the overlap. Then, take it off, make sure it is straight, and measure from the beginning to the overlap.

Please send us a photo of the measuring strip or string.

In conclusion: If you are measuring at home, sending us pictures of your measuring process is a very important step. 

If you need any assistance, please get in touch with us at service@mollyjewelryus.com

4. Sizing & Design Tips

  • For ring sizes smaller than 4US
    Rings with smaller circumferences have tighter curvature, which can put extra stress on the side settings and make side stones more prone to loosening over time.
    We recommend choosing designs with fewer or smaller side stones to ensure long-lasting durability and comfort.

  • For ring sizes bigger than 9US
    Larger rings naturally experience greater structural stress when worn, as the metal band spans a wider circle and endures more bending force during daily wear.
    To maintain proper strength and balance, we suggest choosing styles with a band thickness of at least 1.6 mm. If you notice that the thickness listed on our product page does not meet this specification, feel free to contact us for customization.

RING SIZE CHART