In order to distinguish Natural & Labgrown diamonds, Naturalmark Lab Pvt. Ltd. has seperate brand Labgrownmark for Labgrown diamonds.
Lab-grown diamonds are graded using the same 4Cs (Carat, Cut, Color, and Clarity) as natural diamonds. However, additional steps are required to identify their synthetic origin and growth method (HPHT or CVD). Below is a step-by-step grading process in a laboratory:
Identification & Initial Examination : Before grading, it is essential to confirm whether the diamond is lab-grown or natural.
Cleaning & Preliminary Check : The diamond is cleaned to remove dust and oil. A gemologist examines the stone under magnification to check for synthetic growth features like metallic inclusions (HPHT) or striation lines (CVD).
Screening & Advanced Identification Tests :
UV-Vis Spectroscopy detects color centers unique to lab-grown diamonds.
FTIR Spectroscopy: Confirms the diamond’s chemical composition.
Photoluminescence Spectroscopy: Identifies growth method (HPHT or CVD).
Cross-Polarized Light Test: Checks for strain patterns (lab-grown diamonds show uniform strain).
Carat Weight Measurement : The diamond is weighed on a precision electronic scale with 0.001 carat accuracy.
Color Grading : The diamond is compared against master stones under controlled lighting.
Graded on the D-Z scale.
Special Considerations: HPHT Grown diamonds may have a bluish or yellowish tint while CVD-grown diamonds may have brownish undertones due to nitrogen impurities.
Fluorescence Test: Many lab-grown diamonds exhibit strong fluorescence under UV light.
Clarity Grading : Examined under 10x magnification using a gemological microscope.
Common inclusions in lab-grown diamonds:
HPHT diamonds: Metallic flux inclusions, tiny black specks.
CVD diamonds: Striation lines, pinpoints, or cloud-like inclusions.
Clarity grading : It is graded from FL (Flawless) to I3 (Included).
Cut Grading : Proportions, symmetry, and polish are analyzed using optical measurement tools.
Key parameters measured:
Overall cut grade: Ranges from Excellent to Poor, based on light performance.
Additional Tests & Laser Inscription
Spectroscopic Analysis: Confirms the diamond’s synthetic origin and growth method.
Inclusion Plotting: A clarity diagram is created.
Laser Inscription (if applicable):
Naturalmark Lab Pvt. Ltd inscribes “Labgrownmark” and the report number on the girdle.
Certification & Final Report : A grading report is issued, containing:
4Cs details (Carat, Cut, Color, Clarity), Fluorescence information, Lab-Grown Diamond classification and Growth method (HPHT or CVD)
Final Verification & Quality Control
A senior gemologist reviews the grading to ensure consistency. The Lab grown diamond is securely packaged with the certificate.
Key Differences from Natural Diamond Grading
1. Identification is crucial to distinguish lab-grown from natural diamonds.
2. Growth method (HPHT or CVD) is recorded in the report.
3. Laser inscription is often mandatory for transparency.
How to read a diamond grading report -
Report : It carries a unique report number, an alpha numeric value for that loose diamond or piece of jewellery graded at Naturalmark Lab and is also used by the customer to check its authenticity by putting in the verify report section of our website.
Description : This tells whether the stones are of Natural or synthetic origin and whether the stones are treated or not and the type of treatment (HPHT)
Remarks : Any additional information required will be mentioned in the remarks section.
Shape : It gives details about the shape of the diamond graded.
Dia pcs/Wt : It tells the number of loose diamonds in a packet or a piece of Jewellery. and the total gross weight of loose or studded diamonds.
Color : The color grade in diamond is denoted by Alphabets from D- M , depicting colourless or pure, white to slight yellow and extending till Z and Z+ covering fancy color diamonds. Naturalmark uses a self designed clock to show the color gradation in a diamond. This beautiful clock can be purchased , and can easily explain a laymen about the various colors in which a diamond can be available.
Clarity : Loose diamonds are being graded from FL to I3 clarity.
Dimensions : It indicates diameter (twice) and height in mm. The image of the diamond is shown in the report.
