"Minor oil" means an emerald's fissures were filled with oil to a minor degree. On a lab report that level is usually written as minor clarity enhancement, code F1. GIA says F1 means the treatment has had only a slight effect on the stone's face-up appearance.
Minor is a judgment about how much the filling changes the stone's appearance, made by the lab. It does not rate the emerald's color or overall quality.
TL;DR
F1 is minor, F2 is moderate, F3 is significant.
Labs treat fillers as a group: oils, resins, wax or others. A report can add which filler it identified.
"No oil" is not one single statement. Labs separate an emerald with no visible fissures from one with fissures but no filling.
A minor grade does not set a price by itself.
The Emerald Scale on a Report
Code | Degree of clarity enhancement | What it means |
|---|---|---|
F1 | Minor | GIA: only a slight effect on face-up appearance |
F2 | Moderate | Between the two |
F3 | Significant | GIA: an obvious effect on appearance |
This is our short summary. The full wording is in the LMHC sheet linked below, dated 2012, so a report's own key takes priority.
Where the Words Minor Oil Come From
The shared wording used by labs in the Laboratory Manual Harmonisation Committee, or LMHC, combines a degree with, optionally, the filler identified. Fillers can include colorless to near-colorless oils, resins and wax. So a report may state the degree and also name the filler, and dealers shorten that to "minor oil".
A listing that says "minor oil" is still the seller's phrase. Ask for the report and read its exact line.
What No Oil Really Says
The LMHC sheet separates three statements for an emerald with no filling found:
None is for use only when no fissures are observable.
No fissure filling is for use when fissures are observable.
No indications of clarity enhancement is also for use when fissures are observable.
So two emeralds can both be sold as "no oil" while their reports say different things. As with no indications of heating on ruby and sapphire, the wording reports what the lab found on the day it examined the stone.
Why an Old Report May Not Describe the Stone Today
In June 2026, SSEF warned that emeralds are being cleaned, tested and then refilled after the report is issued. According to National Jeweler, the lab said stones are stripped of resin with strong solvents, reported as having no or minor clarity modification, then refilled with oil or resin and sold with that report. SSEF called presenting them this way fraud, and published photos of one emerald from 2024 and 2026 that it said had clearly been cleaned and refilled in between.
SSEF's advice includes checking whether a fissured emerald has been retested, especially if the report is old or the stone looks unusually clean, and considering a new test. See How to Verify a Gem Lab Report.
FAQ
Is minor oil good for an emerald? It tells you the filling has a slight effect on appearance, according to GIA's definition of F1. It says nothing about color, origin or the rest of the stone, so judge those separately.
What is the difference between minor oil and no oil? Minor oil means filling was found, to a minor degree. No oil means none was found, and the exact report wording depends on whether fissures are visible.
How much more is a no oil emerald worth? We found no reliable public figure, so we do not publish one. See What Is Emerald? for what drives value.
Does F1 tell you the oil type? Not by itself. F1 is the degree. The filler is a separate piece of information that a report may add.
Useful Sources
Carat Brief is editorial and is not investment advice. Get sourced gem prices, free, every Tuesday.