From heirloom sapphires to a newly gifted diamond pendant, there is a special confidence that comes from knowing your gemstones are authentic. In a world where lab-grown stones, imitations, and treated gems are ever more sophisticated, recognising what you own or plan to purchase is both reassuring and financially wise. The good news is that a blend of careful observation, simple non-destructive checks, and professional verification can give you a clear answer.
At Sophie Harley we champion transparency and craftsmanship, and we encourage clients to understand the beauty and character of the stones they wear. Whether you are assessing a family jewel or comparing pieces in a boutique, the following guidance explains what to look for with your own eyes, which instruments offer reliable insight, and when to seek documentation and expert validation.
Start With Visual Clues: What Your Eyes Can Tell You
Begin by observing overall craftsmanship and proportion. Quality gems are often set with precision in well-made mounts, with even prongs, crisp seatings, and a clean finish. Examine the stone under good lighting and rotate it slowly. Genuine gemstones typically show complex, lively light performance: diamond should display bright, sharp scintillation; sapphires and rubies often exhibit rich saturation rather than a flat, inky tone; emeralds reveal a distinct, velvety glow. Very glassy or overly uniform colour, especially combined with soft facet edges, can be a sign of glass or synthetic substitutes.
Magnification is your friend. A jeweller’s loupe (10x) can reveal tell-tale internal features. Natural inclusions may look like tiny crystals, needles, mineral “fingerprints,” or subtle growth lines. Gas bubbles that appear perfectly round and evenly spaced are a common clue for glass imitations. Doubled facet edges, seen when looking through certain stones like zircon or tourmaline, can indicate double refraction and are consistent with many natural species; however, moissanite’s strong double refraction is a key reason it can mimic diamond’s sparkle yet look different under magnification.
Inspect the girdle and the pavilion for seams or layers. Some gems are assembled as doublets or triplets, especially opals and some emerald composites; a visible line between layers, colour concentrations at the edges, or a different material capping the top are indicators. Look for colour zoning as well: many natural sapphires show subtle bands of lighter and darker blue. Perfectly even colour can be desirable, but if combined with other red flags, it may suggest a synthetic origin. Avoid scratch or heat tests at home. They can damage your jewellery and do not conclusively prove identity.
Reliable Testing: From Refractive Index To UV And Thermal Checks
Refractive index is one of the most definitive properties of a gemstone. A refractometer, used with a drop of contact liquid, measures how light bends through a polished facet and can distinguish between species that look similar. For instance, sapphire, spinel, and glass can appear alike to the untrained eye, but their refractive indices differ. A polariscope can then help determine whether a stone is singly or doubly refractive, narrowing identification further. A dichroscope reveals pleochroism, the way some gems show different colours from different directions, common in tourmaline and sapphire.
Spectroscopy provides a diagnostic light fingerprint. A handheld spectroscope can display absorption lines or bands that are characteristic of certain stones, such as chromium lines in ruby or iron-related features in peridot. Longwave and shortwave ultraviolet responses can also be telling. Some diamonds fluoresce blue under longwave UV, while many synthetic rubies fluoresce intensely and evenly. Fluorescence alone is not proof, but in combination with other data it is powerful.
Thermal and electrical conductivity instruments round out modern testing. Diamond testers measure heat conductivity to separate diamond from glass or cubic zirconia, while combined testers can also help distinguish diamond from moissanite, which conducts heat similarly but electricity differently. Hydrostatic weighing can estimate specific gravity, useful for separating similar-looking stones. Each method has limitations and requires clean, accessible facets for accuracy. For conclusive results, a trained gemologist will synthesise observations from multiple tools rather than relying on a single reading.
Certificates, Treatments, And Choosing Trusted Sources
Independent laboratory reports are the gold standard for high-value gemstones. Reputable labs such as GIA, SSEF, Gübelin, GRS, and AGL issue documents that identify the stone, confirm whether it is natural or lab-grown, disclose treatments, and sometimes comment on probable origin. For diamonds, grading reports detail the 4Cs and may include laser inscriptions that match the report number to the stone. For coloured gemstones, origin opinions and treatment disclosures (such as heated sapphire or minor oil in emerald) are essential to value.
Understanding treatments protects both enjoyment and investment. Heat treatment is common and generally stable in sapphires and rubies, while beryllium diffusion, glass filling, or heavy dyeing can significantly affect durability and price. Emeralds are often oiled to reduce visible fissures; reputable disclosures use terms such as none, minor, moderate, or significant. Composite rubies or emeralds that contain large amounts of glass or resin require special care and are valued differently from natural, minimally treated stones. Always ask for written disclosure and documentation.
Finally, buy from jewellers who stand behind their pieces. Clear return policies, transparent descriptions, and access to gemological verification are hallmarks of a trusted source. At Sophie Harley, stones are selected for beauty and integrity, and we welcome informed questions about origin and treatment. Keep invoices, lab reports, and any correspondence; these records support future insurance, valuation, or resale. If you inherit or purchase a notable gem without paperwork, consider an independent laboratory report to establish identity and condition.
Conclusion
Authenticity is a combination of what you can see, what instruments can confirm, and what reputable documentation certifies. With a careful eye for inclusions and craftsmanship, awareness of modern testing, and an understanding of treatments, you can approach every gemstone with confidence and discernment.
If you are feeling inspired to add a meaningful gem to your collection, explore the handcrafted designs at Sophie Harley. Browse our gemstone-adorned rings, pendants, and earrings to discover pieces that blend characterful stones with meticulous artistry, and find a jewel you will treasure for years to come.
