What is a Lab Diamond Certificate? How to Read IGI and GIA Reports

Buying a Lab Grown Diamond Can Feel Surprisingly Technical Once You Start Comparing Certificates.

You May See Terms Such as IGI, GIA, Carat Weight, Color Grade, Clarity Grade, Polish, Symmetry, Fluorescence, Proportions, Clarity Plot, Growth Method, and Post-growth Treatment All Packed Into One Report. If You Know What Those Terms Mean, a Diamond Certificate Becomes Much Easier to Understand and Much Harder to Misread.

A Lab Diamond Certificate, More Accurately Called a Diamond Grading Report, is an Independent Assessment of a Diamond's Identifying Characteristics and Quality. It Gives You a Documented Reference for What You Are Actually Buying, Rather Than Asking You to Rely Only on a Jeweler's Product Description.

But There is an Important Distinction: A Certificate Does Not Tell You Whether a Diamond is Beautiful or Worth the Asking Price. It Tells You What a Gemological Laboratory Found When It Examined the Stone.

So, How Do You Read a Lab Diamond Certificate?

This Guide Walks Through the Major Sections of an IGI Diamond Report and GIA Lab-grown Diamond Report, Explains What Each Number and Diagram Means, and Shows You What to Check Before You Buy.

Why Every Lab Diamond Should Come With a Certificate

A Lab-grown Diamond is a Real Diamond With Essentially the Same Chemical Composition and Crystal Structure as a Natural Diamond. The Important Difference is Its Origin: It is Created Using a Controlled Laboratory Process Rather Than Forming Naturally Underground Over Geological Time.

Because the Stone Can Still Vary Considerably in Cut, Color, Clarity, Proportions and Other Characteristics, Having an Independent Report Gives You a Useful Way to Compare Diamonds.

For Example, Two Lab-grown Diamonds Can Both Be Advertised as 1 Carat, Vs1, E Color, Yet Look Noticeably Different Because Their Proportions, Cut Performance, Polish, Symmetry or Visual Characteristics Are Not Identical.

That is Why a Grading Report Matters.

What Does a Diamond Grading Report Actually Do?

A Diamond Grading Report Documents Characteristics Such as:

• Diamond Shape and Cutting Style
  
• Carat Weight
  
• Measurements
  
• Color Grade
  
• Clarity Grade
  
• Polish
  
• Symmetry
  
• Fluorescence, Where Applicable
  
• Proportion Information
  
• Clarity Characteristics
  
• Laser Inscription Information
  
• Growth Method or Treatment Information, Depending on the Laboratory and Report Type

The Report Also Gives the Diamond a Unique Report Number That Can Generally Be Checked Through the Grading Laboratory's Online Verification System.

Think of It as the Diamond's Technical Identity Card.

It Does Not Replace Seeing the Actual Diamond, but It Gives You a Reliable Reference Point When Comparing Stones.

IGI vs GIA: Which Certificate is More Common for Lab Diamonds?

When Shopping for Lab-grown Diamonds, IGI and GIA Are Two Names You Are Likely to Encounter.

IGI Has a Strong Presence in the Lab-grown Diamond Market and Provides Dedicated Laboratory-grown Diamond Reports That Include Identifying Information, Measurements and 4cs Assessments. IGI Also Notes Growth Process and Treatment Information When Applicable.

GIA Also Offers Laboratory-grown Diamond Services, but Its Current Report Lineup Includes Different Formats, So the Exact Information Shown Depends on the Service Used. Current GIA Offerings Include a Laboratory-grown Diamond Quality Assessment for Qualifying Colorless-to-near-colorless Stones, as Well as Other Laboratory-grown Diamond Report Formats.

That Means the Old Question of “is IGI Always Better Than GIA?” or “is GIA Always Better Than IGI?” is Too Simplistic.

The Better Question is:

What Does the Specific Report Say, and Does the Actual Diamond Match It?

For a Buyer, the Most Important Things Are That the Report is Genuine, the Report Number Matches the Diamond, the Stone's Characteristics Are Clearly Documented, and You Understand Exactly What the Grading Laboratory Has Assessed.

If You Want a Deeper Comparison, See Our Guide: “IGI vs GIA Certified Diamonds: What You Must Know Before You Buy.”

The Top Section: What Report Numbers and Dates Mean

The Top Portion of a Lab Diamond Certificate Usually Contains Some of the Most Important Identifying Information.

Start Here Before Getting Distracted by the 4cs.

Report Number

The Report Number is a Unique Identification Number Assigned to the Grading Report.

This is One of the First Things You Should Check Online.

If the Diamond Has a Laser Inscription on Its Girdle, the Inscription Should Correspond With the Report Number Shown on the Report, Subject to the Specific Laboratory's Inscription Format.

Report Date

The Report Date Tells You When the Laboratory Issued the Report.

A Newer Report is Not Automatically a Better Report, but the Date Can Be Useful When Comparing Documentation or Asking a Seller Whether a Diamond's Report is Current.

Laboratory Name

Check Which Laboratory Issued the Report.

An IGI Report Should Be Verifiable Through IGI's Official System, While a GIA Report Should Be Checked Through GIA'S Report Verification Service.

Do Not Rely Solely on a Screenshot or PDF Supplied by a Seller.

Diamond Identification

The Report Should Clearly Identify the Stone as Laboratory-grown When the Report is for a Lab-grown Diamond.

This Distinction Matters Because a Lab-grown Diamond and a Natural Diamond Can Have the Same Basic Physical and Chemical Characteristics While Having Very Different Origins and Market Positioning.

Shape and Measurements: What to Check First

Before Getting Into Color and Clarity, Look at the Diamond's Shape, Cutting Style and Measurements.

If You Are Buying an Oval, for Example, the Report Should Identify It as an Oval Brilliant or the Applicable Cutting Style. A Round Brilliant, Emerald Cut, Cushion, Pear, Radiant and Oval Diamond Will Naturally Have Different Proportions and Visual Characteristics.

Measurements

Measurements Are Normally Listed in Millimeters.

For Example:  9.01 × 6.05 × 3.72 Mm

These Numbers Represent the Diamond's Length, Width and Depth.

Measurements Become Particularly Useful When Comparing Diamonds With the Same Carat Weight.

A 1-carat Oval Can Look Longer and Larger Face-up Than Another 1-carat Oval Because the Two Stones Can Have Different Length-to-width Ratios and Depth Proportions.

This is One Reason You Should Never Judge a Diamond by Carat Weight Alone.

Length-to-width Ratio

For Fancy Shapes Such as Ovals, Pears, Emerald Cuts and Elongated Cushions, the Length-to-width Ratio Can Help You Understand the Overall Appearance.

For Example, an Oval With a Higher Length-to-width Ratio Will Appear More Elongated, While a Lower Ratio Generally Produces a Broader Look.

There is No Universally Correct Ratio.

The Best Ratio is the One That Matches Your Preferred Shape and How You Want the Diamond to Look on the Hand.

Understanding the 4cs on the Certificate

The 4cs—cut, Color, Clarity and Carat Weight— Are the Foundation of Diamond Grading, but Each One Tells You Something Different.

Understanding How They Appear on the Report Makes It Much Easier to Compare Two Diamonds Intelligently.

1. Carat Weight

Carat Refers to the Weight of the Diamond, Not Its Visual Size.

One Carat Equals 200 Milligrams, and Carat Weight is Usually Recorded to a Precise Decimal Point on a Grading Report.

For Example, a Report Might Show:

Carat Weight: 1.01 CT

That Does Not Automatically Mean the Diamond Will Look Larger Than Another 1.00-carat Diamond.

A Diamond's Face-up Dimensions Depend on Its Measurements and Proportions, So Two Diamonds With Nearly Identical Carat Weights Can Have Different Visual Sizes.

What to Check

Look at:

• Exact Carat Weight
  
• Measurements
  
• Depth
  
• Table
  
• Shape

This Gives You a Much Better Understanding of How Much Diamond You Are Actually Seeing From the Top.

2. Color Grade

For Colorless-to-near-colorless Diamonds, the Traditional D-to-z Color Scale Moves From D, the Highest Level of Colorlessness, Downward Through Increasingly Noticeable Warmth.

Your Certificate May Show Something Like:

Color Grade: E  Or  Color Grade: G

For Many Buyers, the Difference Between Adjacent Color Grades Can Be Subtle When the Diamond is Viewed Face-up, Particularly Once the Stone is Mounted.

But Shape and Setting Can Influence How Color Appears.

Round Brilliant Diamonds, for Example, Tend to Hide Body Color Differently From Elongated Shapes Such as Ovals, Pears and Emerald Cuts.

What to Look for on a Diamond Certificate

Do Not Automatically Assume That the Highest Possible Color Grade is the Best Purchase.

Instead, Consider Whether the Color Grade Looks Good With:

• Your Diamond Shape
  
• Your Chosen Metal
  
• Your Budget
  
• The Overall Appearance of the Stone

A Slightly Lower Color Grade Can Sometimes Give You More Room in the Budget for a Larger Diamond or Stronger Cut Performance.

3. Clarity Grade

Clarity Refers to the Presence of Internal Inclusions and External Blemishes.

Depending on the Grading System and Report Format, You May See Grades Such as:

• FL — Flawless
  
• IF  — Internally Flawless
  
• VVS1 / VVS2
  
• VS1 / VS2
  
• SI1 / SI2
  
• I1 and Lower Categories Where Applicable

A Diamond Can Have a Lower Clarity Grade While Appearing Completely Clean When Viewed Normally.

That is Why the Clarity Grade Should Be Considered Together With the Actual Diamond Images and, Ideally, a Professional Inspection.

4. Cut Quality

Cut is Often Misunderstood.

It is Not Simply Another Version of Color or Clarity.

Cut Relates to How Effectively a Diamond's Facets Interact With Light, and It is Influenced by Proportions, Symmetry, Polish and Facet Arrangement.

A Well-cut Diamond Can Appear Bright, Lively and Balanced.

A Poorly Proportioned Diamond Can Look Dull Even When Its Carat Weight, Color and Clarity Appear Impressive on Paper.

For Round Brilliant Diamonds, the Grading Report May Provide Proportion Information and, Depending on the Laboratory and Report Format, a Cut Assessment.

For Fancy Shapes, You Should Be Especially Careful About Relying on a Single Grade Because Visual Performance Can Vary Significantly Between Stones of the Same Nominal Specifications.

The Proportion Diagram: How to Read It for Cut Quality

The Proportion Diagram is One of the Most Useful Parts of a Diamond Report, Especially When You Are Comparing Round Brilliant Diamonds.

It Can Show Measurements and Proportions Such as:

• Table Percentage
  
• Depth Percentage
  
• Crown Information
  
• Pavilion Information
  
• Girdle Thickness
  
• Culet
  
• Other Proportion Measurements

For Example, a Report Might Show:

Table: 57%  - Depth: 61.5%

Those Numbers Tell You How the Diamond is Proportioned, but They Should Not Be Interpreted in Isolation.

A Table Percentage That Looks Attractive on Paper Does Not Guarantee Beautiful Light Performance.

The Same is True of Depth.

Why Proportions Matter

If a Diamond is Cut Too Deep, Some of the Weight Can Sit Below the Girdle Rather Than Contributing to Visible Face-up Size.

If It is Cut Too Shallow, Light Can Escape Through the Pavilion and Reduce Brightness.

That is Why Proportions Should Be Used as a Screening Tool, Not as the Final Answer.

For a Deeper Look at Round Diamonds, See Our “the Ideal Proportions Checklist for Round Brilliant Lab Diamonds.”

The Clarity Plot: Understanding Red vs. Green Marks

If Your Report Includes a Clarity Plot, Do Not Skip It.

The Clarity Plot is a Diagram Showing Where the Grader Identified Specific Internal or External Characteristics.

On Many IGI-style Diamond Reports, Red Symbols Indicate Internal Characteristics While Green Symbols Indicate External Characteristics.

This is Not a Beauty Score.

It is Essentially a Visual Map of the Characteristics Used to Support the Clarity Assessment.

For Example, the Plot Might Identify:

• Crystals
  
• Clouds
  
• Pinpoints
  
• Needles
  
• Feathers
  
• Cavities
  
• Other Clarity Characteristics

Does a Bigger Clarity Plot Mean a Worse Diamond?

Not Necessarily.

The Number, Size, Location and Visibility of Inclusions Matter More Than Simply Counting Symbols.

A Single Inclusion in an Inconvenient Location Can Sometimes Have More Visual Impact Than Several Tiny Inclusions That Are Difficult to See.

This is Why a Clarity Plot Should Be Considered Together With the Actual Diamond.

What Should You Compare?

When Comparing Two Diamonds With Similar Clarity Grades, Look at:

• The Clarity Grade
  
• The Type of Inclusions
  
• Their Location
  
• Whether They Are Visible in the Diamond Photographs
  
• Whether They Could Affect Durability or Appearance

The Certificate Tells You What Was Identified.

The Photographs and Professional Inspection Help You Understand What That Information Means Visually.

Fluorescence, Polish and Symmetry — Why These Matter

These Three Terms Are Easy to Overlook Because They Often Appear Lower on the Report, but They Still Provide Useful Information.

Fluorescence

Fluorescence Describes How a Diamond Reacts When Exposed to Ultraviolet Radiation.

A Report May Describe Fluorescence as:

• None
  
• Faint
  
• Medium
  
• Strong
  
• Very Strong

Fluorescence is Not Automatically Good or Bad.

In Some Diamonds, It Can Have Little Practical Effect on Appearance. In Others, Particularly Depending on the Diamond's Color and Fluorescence Strength, It May Influence How the Stone Looks Under Certain Lighting Conditions.

So Don't Reject a Diamond Simply Because the Certificate Mentions Fluorescence.

Instead, Consider the Actual Stone.

Polish

Polish Refers to the Quality of the Diamond's Surface Finish After Cutting and Polishing.

You May See Grades Such as:

• Excellent
  
• Very Good
  
• Good

A Strong Polish Grade is Desirable Because Poor Surface Finishing Can Affect the Way Light Interacts With the Stone.

Symmetry

Symmetry Describes How Accurately the Diamond's Facets and Overall Structure Are Aligned.

Good Symmetry Helps Create Balanced Light Performance and a Visually Pleasing Appearance.

For an Engagement Ring, Polish and Symmetry Are Usually Supporting Factors Rather Than Reasons to Buy a Diamond on Their Own.

Post-growth Treatment Alerts: What They Mean for HPHT Diamonds

This is One of the Most Important Sections to Understand When Buying a Lab-grown Diamond.

Lab-grown Diamonds Can Be Produced Using Different Growth Methods, Including CVD (Chemical Vapor Deposition) and HPHT (High Pressure, High Temperature).

A Report May Identify the Growth Method, Depending on the Laboratory and the Specific Report Type.

Some Lab-grown Diamonds Can Also Undergo Treatment After Growth to Modify Their Color.

GIA Explains That Its Laboratory-grown Diamond Reporting Can Identify Growth Method and Post-growth Treatment on Applicable Report Formats, While Current GIA Dossier Reporting is a Streamlined Format That Omits Those Particular Fields.

So if You See a Phrase Such as:

“Indications of Post-growth Treatment”

Do Not Assume That It Means the Diamond is Fake.

It Means You Should Understand Exactly What Treatment Has Been Identified or Reported.

Why Does Post-growth Treatment Matter?

Treatment Can Affect How a Diamond is Described and How You Compare It With Another Stone.

If a Diamond Has Undergone Post-growth Treatment, That Information Should Be Disclosed Rather Than Hidden.

For Buyers, Transparency is the Key.

If You See a Treatment-related Comment on the Report and Do Not Understand It, Ask the Seller to Explain the Exact Wording Before Purchasing.

How to Verify a Diamond Certificate is Real Online

Never Assume a Certificate is Genuine Simply Because the Document Looks Professional.

One of the Easiest Checks You Can Perform Before Buying is to Verify the Report Number Directly Through the Grading Laboratory.

Step 1: Find the Report Number

Locate the Unique Report Number on the Certificate.

Make Sure You Enter It Carefully.

Step 2: Go Directly to the Laboratory's Website

For an IGI Report, Use IGI's Official Report Verification Service. IGI Provides an Online Tool Where Consumers Can Enter the Report Number or Scan the QR Code to Verify the Report.

For a GIA Report, Use GIA'S Official Report Check Service, Which Allows You to Compare the Report Information With the Record in GIA'S Database.

Do Not Rely on a Link Sent by an Unknown Seller if You Can Navigate Directly to the Laboratory's Official Website Yourself.

Step 3: Compare Every Important Detail

Once the Report Appears Online, Compare It With the Physical or Online Listing.

Check:

• Report Number
  
• Lab-grown Identification
  
• Carat Weight
  
• Shape
  
• Measurements
  
• Color
  
• Clarity
  
• Polish
  
• Symmetry
  
• Fluorescence
  
• Treatment Information
  
• Laser Inscription, Where Applicable

The Details Should Make Sense Together.

Step 4: Check the Laser Inscription

Many Lab-grown Diamonds Are Laser-inscribed on the Girdle With Identifying Information.

The Inscription is Extremely Small and Generally Requires Magnification to See Clearly.

If the Diamond Has an Inscription, Ask the Jeweler to Show You a Magnified Image or Confirm It Under a Microscope.

A Mismatch Between the Inscription and the Report Number is a Serious Reason to Stop and Investigate Before Buying.

Step 5: Compare the Actual Diamond

A Genuine Report Does Not Automatically Mean the Diamond is the Right Diamond for You.

The Certificate Can Be Authentic While the Stone Still Has:

• Unattractive Proportions
  
• Visible Inclusions
  
• Uneven Shape
  
• Weak Light Performance
  
• Excessive Bow-tie in an Oval
  
• Poor Visual Spread
  
• Other Appearance Issues

The Report Verifies Information.

Can a Diamond Certificate Be Faked or Forged?

Yes, Documents Can Be Manipulated or Misrepresented, Which is Why Online Verification is So Important.

A Copied PDF, Edited Screenshot or Convincing-looking Certificate is Not Enough Evidence by Itself.

The Safest Approach is to Verify the Report Directly With the Issuing Laboratory.

Even Better, Compare the Verified Report With the Physical Diamond's Identifying Information, Including the Laser Inscription Where Applicable.

If the Seller Refuses to Provide a Report Number, Avoids Verification, or Gives You a Certificate That Does Not Match the Stone, Treat That as a Major Warning Sign.

A Reputable Seller Should Have No Problem With You Checking the Report.

Does Every Lab Diamond Come With a Certificate?

Not Necessarily.

Some Diamonds May Be Sold Without an Independent Grading Report, Particularly Smaller Stones or Jewelry Pieces Where the Individual Center Stone Has Not Been Separately Graded.

But if You Are Buying a Significant Lab-grown Center Diamond for an Engagement Ring, an Independent Grading Report Can Make Comparison and Verification Much Easier.

If a Diamond is Advertised With a Specific Grade Such as 1.50 CT E Vs1, Ask Whether Those Grades Come From an Independent Laboratory Report or Are Simply the Seller's Description.

That Distinction Matters.

Final Thoughts: A Certificate is a Tool, Not the Whole Buying Decision

Learning How to Read a Lab Diamond Certificate Can Make the Buying Process Much Less Confusing.

You Don't Need to Become a Gemologist.

You Simply Need to Understand What the Report is Telling You, Verify That the Report is Genuine, and Know Which Details Deserve Closer Attention.

Start With the Report Number, Shape, Measurements and 4cs. Then Look Deeper at the Proportions, Clarity Plot, Fluorescence, Polish, Symmetry and Any Comments About Growth Method or Post-growth Treatment.

Most Importantly, Don't Make the Mistake of Choosing a Diamond Based on the Certificate Alone.

The Best Purchase is the One Where the Report Checks Out, the Diamond Looks Beautiful to You, the Proportions Make Sense, and the Price Feels Appropriate for What You Are Actually Getting.

Frequently Asked Questions

Q.  What is an IGI Certificate for a Lab Diamond?
A.  An IGI Certificate, More Accurately Called an IGI Laboratory-grown Diamond Report, is a Grading Document That Records Identifying Characteristics and Quality Information for a Lab-grown Diamond. Depending on the Report Type, It Can Include the Diamond's Shape, Measurements, Carat Weight, Color, Clarity, Polish, Symmetry, Fluorescence and Other Relevant Information. IGI Also Provides an Online Report Verification System.

Q.  Is IGI or GIA Better for Lab Diamonds?
A.  Neither Should Be Considered Automatically “Better” Without Looking at the Specific Report and Diamond. IGI Has Extensive Laboratory-grown Diamond Reporting, While GIA Currently Offers Several Laboratory-grown Diamond Service Formats With Different Levels of Information. The Most Important Factors Are Report Authenticity, Transparent Grading Information, a Matching Diamond and the Actual Visual Quality of the Stone.

Q.  How Do I Verify a Diamond Certificate is Real?
A.  Find the Report Number and Enter It Directly Into the Issuing Laboratory's Official Verification System. IGI Provides an Online Report Verification Tool, While GIA Provides Report Check for Verifying Information Against Its Database.

Q.  What Does the Clarity Plot on a Certificate Show?
A.  A Clarity Plot is a Diagram Showing the Location and Type of Internal Inclusions and External Blemishes Identified During Grading. On IGI Reports, Red Symbols Generally Indicate Internal Characteristics and Green Symbols Indicate External Characteristics.

Q.  What Does Fluorescence Mean on a Diamond Report?
A.  Fluorescence Describes a Diamond's Reaction to Ultraviolet Light. It May Be Reported as None, Faint, Medium, Strong or Another Applicable Grade. Fluorescence is Not Automatically a Positive or Negative Characteristic, So It Should Be Considered Together With the Diamond's Color and Actual Appearance.

Q.  What is a “Post-growth Treatment” Alert on a Lab Diamond Certificate?
A.  A Post-growth Treatment Alert Indicates That the Report Has Identified or Commented on Treatment Performed After the Diamond Was Grown. Some Laboratory-grown Diamonds Can Undergo Treatment to Modify Their Color. The Exact Wording and Whether Treatment Information is Included Depends on the Laboratory and Report Format.

Q.  What is the Laser Inscription Number on a Diamond Certificate?
A.  A Laser Inscription is Microscopic Identifying Information Placed on a Diamond's Girdle. For Applicable Lab-grown Diamonds, It Can Include the Grading Laboratory's Report or Assessment Number and an Indication That the Stone is Laboratory-grown. It Can Be Viewed Under Magnification and Used as an Additional Way to Match the Physical Diamond With Its Report.