Gemmological laboratories

Gives the trade-standard tenfold magnified view of a stone's surface and near-surface interior.

Ten times magnification is the reference condition under which clarity is described in the diamond trade, so it sets the baseline for what counts as an eye-visible rather than a magnification-visible feature.

Reveals internal inclusions, growth structures, fractures and residues at magnifications typically between 10x and 90x, with immersion in a liquid to suppress surface reflections.

Inclusion scenes are the primary evidence a laboratory uses to separate natural from synthetic material and to recognise heat treatment or fracture filling.

Measures refractive index and birefringence by reading the critical angle of light at a polished facet.

Refractive index narrows a stone to a small set of candidate species and is one of the fastest checks that a stone is the material it is described as.

Determines whether a material is singly refractive, doubly refractive or aggregate, and shows strain and optic figures between crossed polarising filters.

Optic character separates whole groups of gems and imitations from one another before any costly analysis is commissioned.

Compares a stone's weight in air with its weight suspended in water to derive its density relative to water.

Density distinguishes look-alike species of similar colour and can be measured on an unmounted stone without any polished facet.

Shows how a stone transmits in two narrow bands of the visible spectrum when viewed through a paired-filter assembly.

It is a rapid sorting aid for emerald and its imitations and for some dyed material, though a filter reaction on its own never settles an identification.

Disperses light transmitted through or reflected from a stone so that absorption lines and bands can be seen directly.

Characteristic absorption features point to the colouring element present, which supports species identification and flags some dyes and synthetics.

Records the colour and strength of fluorescence and any phosphorescence under 365 nm and 254 nm excitation.

Fluorescence behaviour separates many natural stones from their synthetic counterparts and reveals filled fractures, some dyes and assembled stones.

Records absorption across ultraviolet, visible and near-infrared wavelengths to map the electronic transitions responsible for colour.

It underpins natural versus synthetic calls and the detection of colour treatment in stones such as diamond, corundum and beryl.

Records infrared absorption arising from molecular vibrations, including water, hydroxyl, carbon dioxide and polymer species inside a stone.

Infrared signatures identify resin and polymer fillers in emerald and jadeite and separate several natural and synthetic materials by their growth chemistry.

Reads the inelastic light scattering signature of a material to give a structural fingerprint of the host and of individual inclusions.

It identifies mineral inclusions in place without opening the stone, which is central to origin work and to recognising fillers and synthetic growth residues.

Measures light emitted after laser excitation, usually at cryogenic temperature, to detect defect centres present at very low concentrations.

It is the principal method for separating laboratory-grown from natural diamond and for detecting high pressure high temperature treatment.

Determines the major and minor chemical elements present by reading the characteristic X-ray fluorescence a sample emits under X-ray excitation.

Chemical fingerprints separate species and varieties, flag some treatments and give a first indication of geographic source without marking the stone.

Vaporises a microscopic volume of material with a laser and measures trace element concentrations down to parts per million or lower.

Trace element ratios compared against a reference database are the quantitative basis of most country-of-origin opinions for ruby, sapphire and emerald.

Images internal structure by differential X-ray absorption, in two dimensions or as a reconstructed three-dimensional volume.

It is the standard means of separating natural from cultured pearls by revealing the internal growth structure and any bead nucleus.

Determines crystal structure from the angles at which a sample diffracts a monochromatic X-ray beam.

It confirms the crystalline species where optical and chemical data are ambiguous, including polycrystalline and opaque materials such as jade.