Start with identity
Check the report number, date, shape, measurements, and laser inscription if present. Make sure the report belongs to the stone in front of you.
Read the 4Cs together
Do not isolate one grade. A D colour with poor make can be less desirable than a G colour with excellent performance. A large carat with visible inclusions can be harder to trade.
Use the plot and comments
The clarity plot shows inclusion type and position. Comments can reveal details that affect confidence, such as additional clouds or surface graining.
Decision table
Use the details, not a shortcut.
| Report field | Why it matters | Question to ask |
|---|---|---|
| Report number | Identity check | Does it match online and inscription? |
| Measurements | Face-up size and make | Does the spread suit the carat? |
| 4Cs | Core quality language | Do the grades work together? |
| Fluorescence | Appearance and trade impact | Is it visible in this stone? |
| Plot/comments | Clarity risk | Where are the inclusions? |
Direct answers
Common questions
Is GIA the only certificate that matters?
GIA is one of the most recognised diamond grading authorities. Other labs exist, but buyers often price them differently.
Can a certificate be fake?
A report number can be copied. Verify the report online and match the stone, measurements, and inscription.
Will Prodiam check a certificate?
Yes. Prodiam can review certified stones as part of a buying or valuation conversation.