A structured 12-lesson course in gemstone identification, built from
a reference database of 132 species. Start with what identification actually is,
finish by working an unknown stone through the full sequence. No fee, no account,
no enrolment.
What this is. A genuine curriculum in the technique of gem
identification — the instruments, the measurements, and the order to use them in.
Everything it links to is published on this site and free to read.
What it is not. This is not an accredited qualification and it
does not replace GIA, Gem-A or FEEG. Those award recognised professional credentials
assessed on graded stones under exam conditions, and nothing online substitutes for
that. If you intend to work in the trade, you will want one of them. This course
exists so you can learn the craft — and find out whether you love it — before you
commit several thousand dollars to finding out.
Deciding whether to do this at all?How to become a gemologist
lays out what each route costs, what the work pays, and how long it actually takes — and free gemology courses online lists everything that costs nothing first —
from the providers' own catalogues and filings rather than from anyone selling a course.
The course
1
What gem identification actually is
Why appearance is the weakest evidence there is, and what replaces it.
Two stones that look identical can be a fine ruby and an ordinary garnet worth a tiny fraction of it. Colour, cut and clarity tell you almost nothing about species, because different minerals share the same appearance and the same mineral appears in many colours. Identification works the other way round: you measure physical constants that do not change with appearance — how much the stone bends light, how dense it is, how it behaves under polarised light — and eliminate everything those measurements rule out. You rarely "recognise" a stone. You narrow 132 candidates down to one.
Colour is the weakest evidence and the strongest filter. Both are true.
Never conclude from colour — and be careful about eliminating on it either. Body colour shifts with lighting and treatment, and a single species can occur across several colours, so a stone you rule out for being "too green" can still be the answer. What colour is good for is deciding where to look first: group the possibilities by body colour, then let a measurement decide among them. That is why this tool ranks candidates by colour but never removes one for it.
The single most discriminating instrument in the kit.
Refractive index is a physical constant set by a mineral's atomic structure. One good reading typically cuts the field further than every other test combined. This lesson covers taking a reading, why a shadow edge forms at all, the sliding technique that gets you a clean edge, and what "over the limit" means — a standard refractometer reads to about 1.81, which is the ceiling of the contact liquid rather than of the stone. OTL is a result, not a failure.
The second measurement, and the one that finishes most identifications.
Specific gravity is density relative to water, measured by hydrostatic weighing: weigh the stone in air, then suspended in water. It works on rough and irregular stones with no polished facet — exactly the ones a refractometer struggles with. RI and SG together usually reduce the candidate list to one or two species.
Singly or doubly refractive — a fast, decisive split.
A polariscope tells you whether light travels through the stone at one speed or two. It is the cheapest instrument on this list, it takes seconds, and there is nothing to calibrate — but it is a fork rather than a filter: it roughly halves the field, from 132 species to a median of 75. It will not name a stone and it will not get you close to one. What it gives you is a decision nothing else cheap will make, on stones a refractometer cannot even read. On a doubly refractive stone you then record two refractometer readings, and the difference between them, the birefringence, is diagnostic in its own right.
Some doubly refractive stones show different body colours along different crystal directions. A dichroscope makes that visible in seconds, and trichroism — three distinct colours — is only possible in a biaxial stone, which is a genuine structural deduction rather than an impression.
Useful, wildly over-trusted, and worth learning properly.
Many stones glow under UV, and the response can support an identification or flag a treatment. It is also the test beginners over-read: fluorescence is variable within a species, so it corroborates rather than decides. Learning where it is diagnostic and where it is noise is most of the skill.
A Chelsea filter is a fast screen for a few specific separations. A spectroscope goes further and shows the absorption pattern produced by the elements colouring the stone — the closest thing in a field kit to reading its chemistry directly.
The famous property that working gemologists mostly avoid using.
Every beginner's guide leads with the Mohs scale. Real practice barely uses it, because a scratch test damages the stone and a destructive test on someone else's property is not an option. Learn the scale for what it tells you about durability, wear and setting — not as an identification step.
Putting the sequence together on an unknown stone.
Order matters: observe, then measure the cheap decisive things first, and stop when the evidence converges. This lesson walks the whole sequence on a stone you have never seen, including how to record observations so the reasoning stays auditable — which is what separates an identification from a guess.
Same species, same constants, entirely different value.
A synthetic ruby is really ruby: identical RI, identical SG. Separating grown from mined is a different discipline built on inclusions, growth structures and fluorescence patterns rather than constants — and it is where most of the money and most of the mistakes are.
A handful of pairs account for most misidentifications. Learning them by their separations — which single test splits each pair — is worth more than memorising a hundred species you will never encounter.
Practise what you have read. The Loupewise app takes your actual
measurements and shows which of the 132 species remain consistent with them — and
which test eliminates the most candidates next.
Yes. All 12 lessons and the full reference database of 132 species are free to read, with no enrolment and no account. Loupewise sells a subscription for the identification app and practice exams; the course itself is not gated.
Does this replace a GIA or Gem-A qualification?
No, and it does not pretend to. Those are recognised professional credentials assessed on graded stones under exam conditions. This teaches the underlying technique so you can decide whether the work suits you before committing to a programme.
Do I need to buy instruments to start?
Not for the first two lessons. From lesson 3 you get far more out of it with a refractometer and a way to weigh a stone in water. Reading first is the cheapest way to decide whether the kit is worth buying.
How long does it take?
It is self-paced. Reading through takes a few hours; acquiring the skill takes practice on real stones, which is why every lesson points at data and drills you can work with afterwards.