Diamond certification

A grading report is the only thing between you and a seller’s word. For any meaningful purchase, insist on one. The question is whose.

The six labs that show up in retail today aren’t equivalent. They calibrate their scales differently, which means the same stone can carry meaningfully different grades depending on who graded it. Below, the honest position the trade actually takes — not the marketing copy the labs publish about themselves.

The labs

Why grades differ

Grading is a human judgment with consistent biases by lab. The same stone graded by GIA and EGL might come back GIA G/VS2 and EGL E/VVS2 — not because either lab is lying, but because their internal calibration shifts what "G" means against their master stones. The difference shows up in resale: insurers and trade buyers reprice EGL stones to a GIA- equivalent grade, knocking 20–40 % off the asking price.

What a report includes

Every modern grading report ships with:

• The four Cs — cut, color, clarity, carat
• Measurements (length × width × depth in mm)
• Proportions diagram with table %, depth %, crown angle, pavilion angle
• Plotted inclusion map
• Polish + symmetry grades
• Fluorescence (none / faint / medium / strong / very strong)
• For lab-grown stones, growth method (HPHT or CVD) and any post-growth treatments

The good reports also include:

• Cut-grade overall (GIA round only; AGS pre-2022; GCAL all shapes)
• A photo of the stone (GCAL, GIA on request)
• Lab-grown disclosure on the girdle inscription (a microscopic etched "LG" or full lab name, visible at 10×)

How to read a report

A working buyer checks five things first:

1. The report number matches the girdle inscription. Look at the stone under a loupe — the inscription should be the last few digits of the report number. If it doesn’t match, the cert is for a different stone. Rare but exists.
2. The cut grade. Excellent or Very Good only.
3. Polish + symmetry. Both Excellent for top tier; Very Good is fine.
4. The inclusion plot. A few small inclusions near the edge are ideal; a single large one near the table is the worst position.
5. Fluorescence. Strong + D/E/F = potential issue. Otherwise ignore.

What we accept

Pieces with center stones in our catalog ship with GIA or IGI reports by default. AGS, GCAL, and HRD on request. EGL we don’t accept on consignment because the calibration difference creates a fairness problem on resale — if you bought a stone from us and later try to trade it back, an EGL grade would be revalued to a GIA-equivalent and neither of us wants the surprise.