How to read a lab report

A laboratory report is the closest thing the coloured stone trade has to a common language, and it is routinely misread. A report identifies a stone and records what a laboratory observed on a particular date. It does not grade beauty, it does not set a price and it does not promise that the stone in front of you is the stone that was tested. Reading one line by line takes a few minutes and prevents most expensive misunderstandings before they start.

Start with the header

Every report carries a number, a date of issue and the name of the issuing laboratory. The number is your first tool: the labs the trade relies on operate an online report check where entering it returns a summary of the original document. If a laboratory has no way to verify its own paper, weigh that before you weigh the stone. The date matters too. A report describes the stone as it was on that day, and stones are recut, re-oiled and remounted between owners.

The identification block

The species and variety lines state what the stone is: corundum, variety sapphire; beryl, variety emerald. The word natural in this section means the stone grew in the ground rather than in a factory. It says nothing about treatment, which is recorded separately and is the more consequential line.

Weight is given in carats to two decimal places, with measurements in millimetres and a note of shape and cutting style. These figures must match the stone in front of you. Colour is described in the laboratory's own vocabulary; there is no universal grading scale for coloured stones, so one house's vivid blue is not calibrated against another's. Trade colour names such as pigeon's blood or padparadscha appear only where a lab maintains written criteria for them, and those criteria differ from lab to lab.

The treatment line

This is the single most important line on the document, and the wording is deliberate. No indication of heating means the laboratory found no evidence of thermal treatment. Indications of heating means it did. Codes and comments extend the story: notes on heat, on residues in fissures, and for emerald a grade for the amount of filler present. If the treatment line is absent, or vague, or the report comes from a laboratory you cannot look up, the prudent reading is that the stone is treated and should be priced as such.

Origin is an opinion

Where a report states a country of origin, it is an expert opinion formed from the stone's inclusions and trace-element chemistry, matched against the laboratory's reference collection. It is not a certificate of export and not a fact. Respected laboratories occasionally disagree about the same stone, which is why important goods often travel with two reports. Treat a confident origin line as evidence, and treat a dealer who calls it proof with more care.

Check the paper against the stone

A genuine report travelling with a different stone is the most common form of paperwork fraud, and the defence is procedural rather than clever. Verify the report number through the lab's online check. Weigh the stone if you can, and measure it; a recut leaves the old dimensions stranded on the page. Where the report includes a photograph or an inclusion map, hold the stone to the light and find what the plot says should be there. None of this requires a gemmologist, only patience.

What the report cannot tell you

A report will not tell you whether the stone is well cut for its material, whether the colour holds in evening light, or what it is worth. Two stones with identical wording can sit far apart in the market. The document clears the ground so that judgement can work: it removes doubt about identity and treatment and leaves you free to judge the stone as a stone.

GemsVerified's role sits one step behind the paper. We verify whether a dealer certifies with recognised laboratories and discloses treatments as a condition of admission, and we verify dealers rather than individual stones. The report remains the lab's word. Learn its grammar before you rely on it.