Lab Equipment

The spectroscope records which wavelengths of visible light a gem absorbs. Strong selective absorption bands are diagnostic: the 693 nm doublet in ruby, the 450 nm band in synthetic blue spinel, the 415 nm line in cape diamonds. Each species produces a characteristic pattern determined by the transition-metal impurities or rare-earth elements present in its crystal structure. The spectroscope calculator on this page displays the expected absorption pattern for 16 commonly encountered gem species, drawing from a curated reference table that lists band positions, relative strengths, and the diagnostic significance of each line. Viewing known patterns before working at the bench helps calibrate the eye and sets a reliable expectation for what a positive identification looks like.

The band-matcher inverts this workflow. Rather than looking up a known species and reading off its bands, you enter the wavelengths you actually observe and the tool returns the species whose reference pattern best matches your input. Matching is tolerance-windowed; a band recorded at 692 nm will still match the 693 nm ruby reference, and selective diagnostic bands are weighted more heavily than broad general-absorption regions. This makes the band-matcher especially useful when a stone shows one strong diagnostic line alongside several weaker features that might be confused for another species. The output lists confidence-ranked candidates, not a single forced answer, which mirrors the conditional reasoning a trained gemmologist applies at the bench.

UV fluorescence adds a complementary data point without any contact with the stone. A strong blue long-wave (LWUV) reaction in diamond, absent under short-wave (SWUV), points away from moissanite or cubic zirconia. Conversely, a strong SWUV reaction with weak or absent LWUV is characteristic of certain synthetic ruby flux products. The UV fluorescence lookup parses the freeform fluorescence descriptions stored in the mineral database (for example, "inert to strong blue LWUV, weak yellow SWUV") into structured fields: LWUV colour and intensity, SWUV colour and intensity, and a phosphorescence flag for materials such as natural hyalite opal that continue to glow after the UV source is removed. Intensity is scored on a four-step scale (inert, weak, moderate, strong) to allow ranked comparison across species.

Together the spectroscope and UV fluorescence instruments cover complementary parts of the electromagnetic spectrum and together with RI and SG they form the core analytical toolkit of the FGA Diploma practical examination. These tools are designed to function as both learning aids and bench references: they explain the underlying physics, display the reference data, and support the step-by-step reasoning process that moves an observation toward a confident, defensible identification.