Gemology Hub | Gemstone & Mineral Identification Guides

A ruby’s inclusions can offer clues about its geological history. However, similar-looking inclusions can occur in stones from different places. Early research on rubies from Montepuez, Mozambique, makes this limitation especially easy to understand. What SSEF observed In its 2010 Facette, SSEF described a preliminary investigation of six small samples. Observations included twinning, fissures, crystal inclusions and fine rutile features. The article noted that the internal appearance could resemble Mogok-type rubies from Myanmar. This similarity is valuable for learning, but it does not make the two origins interchangeable. An inclusion pattern associated with a famous deposit may also occur elsewhere. The 2012 SSEF news slides reinforce this point with further Mozambique ruby examples. Why one inclusion cannot locate a mine A laboratory compares multiple microscopic features with chemical and spectroscopic evidence and documented reference samples. The strength of an origin op...

A synthetic spinel is grown by people but has the identity of spinel. It is different from a material that only imitates spinel’s appearance. Flux-grown red spinel is a useful example of why a correct mineral identification does not always establish natural origin. Why routine measurements may overlap SSEF’s 2009 study reported flux-grown red spinels with refractive index and density similar to natural spinel. Their attractive appearance and fluorescence were also insufficient for reliable separation. A familiar result on a basic gem test therefore did not settle the formation question. What the researchers examined Microscopy revealed cavities containing flux residues, sometimes with gas bubbles, and a metallic flake in one specimen. Chemical and spectroscopic observations helped support the interpretation. Brown material inside a fissure must not automatically be labelled flux. Natural spinel can contain other brownish substances, and a similar-looking feature may have a diffe...

The outside of a pearl can look convincing while its centre holds the most useful identification clues. X-ray microtomography, often called micro-CT, helps laboratories examine these hidden structures in three dimensions without cutting the pearl open. From a flat image to virtual slices A conventional radiograph projects internal features onto a flat image. Structures can overlap in that view. Micro-CT uses multiple X-ray views to reconstruct the interior, allowing the analyst to inspect virtual sections in different directions. SSEF’s 2009 article describes how this approach helped investigate pearl growth features. It highlights difficult beadless cultured pearls, for which a clearer view of the central region can be particularly useful. What can the images show? Cavities, fissures and growth structures can become easier to understand when viewed from several angles. The analyst can ask whether a line belongs to one cavity or whether several different features overlap. This p...

Beryllium diffusion is a sapphire treatment, but detecting a trace of beryllium is not automatically the same as proving that treatment. The context of the result matters. This distinction is especially useful when reading claims about highly sensitive chemical tests. A natural example in SSEF research In its 2008 Facette, SSEF described a sapphire–chrysoberyl intergrowth from Madagascar. The study confirmed that low trace amounts of beryllium can occur in natural untreated sapphire. The researchers discussed its relationship with other elements and possible tiny inclusions. That finding does not mean beryllium diffusion is undetectable. It means a laboratory must distinguish natural occurrences from evidence consistent with artificial introduction. A simple present-or-absent rule loses that important detail. What a laboratory considers Sensitive chemical methods can examine very small concentrations and differences within a stone. Microscopic features and the distribution of ch...

A gemstone’s colour depends partly on which wavelengths of light it absorbs and which remain available to reach our eyes. UV-Vis spectroscopy measures this interaction. It turns a colour observation into a pattern that a gemologist can study and compare. What is an absorption spectrum? An absorption spectrum shows how strongly a material absorbs light at different wavelengths. Peaks and bands can provide information about colour-producing elements or other features inside a crystal. Some useful information lies outside the light we can see. SSEF’s 2008 article explains a portable instrument developed for testing away from the main laboratory. It discusses applications to colour research and supporting evidence for sapphire origin analysis. The historical equipment specifications should not be assumed to describe all instruments used today. Why orientation can matter The spectrum must be measured and interpreted under suitable conditions. The observed colour and absorption behavi...

An intense blue or green-blue tourmaline can be beautiful without revealing the country where it formed. Copper-bearing tourmalines from Brazil and parts of Africa can have similar appearances. Colour is therefore an unreliable shortcut for geographic origin. What trace elements can reveal SSEF’s 2007 article compares material from Brazil, Nigeria and Mozambique. It discusses trace-element patterns, including lead, gallium and bismuth, studied with methods such as LA-ICP-MS. These are small chemical clues rather than features visible to the naked eye. The article notes substantial overlap in chemical composition. Useful distinctions emerge from careful comparisons and data interpretation, rather than a rule that one element always identifies one country. Why reference samples matter A laboratory needs reliable samples from known sources to interpret the chemistry of an unknown stone. A measurement becomes much more useful when it can be compared with a documented reference colle...

Melee diamonds are small diamonds used in groups, often in watches and jewellery. Checking thousands of tiny stones creates a different practical problem from grading one large diamond. A laboratory needs a clear plan for what to inspect and how to report the result. Why use a representative sample? SSEF’s 2007 article explains quality control using a representative sample from a lot. This approach depends on a suitably defined, reasonably homogeneous batch and clear quality criteria. It does not mean that every stone has received an individual grade. Colour, clarity and cut still matter. Tiny size makes some observations harder, so the way results and uncertainty are communicated is important. A sample report should be read in the context of the sampling plan. What does AQL mean? An acceptable quality level, or AQL, is used with a sampling plan to decide whether a lot meets an agreed acceptance rule. The buyer’s chosen rule affects the outcome. It should not be read as a guaran...