Practical Guide for Identifying Common Gemstones in Everyday Settings
In the captivating world of gemstones, understanding their properties and identifying them correctly is an essential skill for both collectors and professionals alike. From the enchanting pleochroism of tanzanite, iolite, alexandrite, and sapphire, to the intricate carvings of jadeite, these precious stones hold a world of wonder that extends far beyond their shimmering surfaces.
However, identifying some gem species can be a challenge due to their similarity to various materials. For instance, turquoise, jet, and jadeite share characteristics that make them hard to distinguish from one another. Similarly, pearls, with their overlapping sizes and appearances, can cause identification difficulties, particularly between natural, freshwater, Akoya, and South Sea cultured pearls.
Fear not, for gemologists have developed a suite of techniques to tackle these identification conundrums. One such method is refractive index measurement, using a refractometer to measure how a gemstone bends light. For example, genuine sapphires typically have a refractive index between 1.76 and 1.78.
Spectroscopy, another technique, involves analysing the absorption and transmission of light within a gemstone. This can reveal distinctive absorption lines caused by trace elements, helping gemologists verify if a stone is naturally occurring or artificially enhanced.
Under UV light, authentic gemstones often exhibit specific fluorescence patterns. For example, genuine sapphires typically show weak to moderate fluorescence, while synthetic or treated sapphires may not fluoresce or display abnormal patterns.
Gemmologists also examine a gemstone's optical properties, such as birefringence, dispersion, and specific gravity, along with its physical properties like hardness, cleavage, and fracture. These characteristics can help distinguish between natural and synthetic gemstones.
Certification from accredited institutions like the Gemological Institute of America provides authoritative assurance of a gemstone's authenticity and quality. Examination with magnification, whether through a jeweler's loupe or microscope, can also reveal inclusions, growth patterns, or other characteristics that distinguish natural from synthetic stones.
For some gemstones, like sapphires, a scratch test can be used. Genuine sapphires resist scratches on an unglazed porcelain surface, while softer imitations may show scratches.
Gem testing laboratories have adopted new methods based on modern scientific equipment to deal with the problems arising from new types of gemstone treatment and synthesis. As gemmologists gain experience and handle more stones, their confidence in identification grows.
However, there are recalcitrant gemstones that cannot be identified by routine inspection and testing. In such cases, structures, the absence of structures, surface and internal features, and measurable properties can help recognize or eliminate many gemstone simulants.
With knowledge, experience, instincts, and a keen eye, gemmologists can identify gemstones using properties such as pleochroism, fire, refractive indices, birefringence, and more. For example, a loupe can be used to identify many stones, such as sunstone, by observing its oriented, rounded-looking, opaque copper coloured or translucent orange, iridescent inclusions.
Gemstone identification practices have been around for centuries, and today, courses like the Gem-A Gemmology and Diamond Diplomas offer the information and skills needed to handle gemstones sensibly and keep abreast of current developments in gemmology. So, whether you're admiring a fish carved from jadeite or a stunning sapphire ring, you can now appreciate the art and science behind their identification.
- Certified gemmologists use various techniques, such as refractive index measurement, spectroscopy, and UV light examination, to identify gemstones accurately.
- Examinations with magnification or microscopy can reveal inclusions, growth patterns, or other characteristics that distinguish natural gemstones from synthetics.
- Modern gem testing laboratories employ cutting-edge scientific equipment to tackle the identification challenges posed by emerging gemstone treatments and synthesis.
- Courses like the Gem-A Gemmology and Diamond Diplomas provide the necessary knowledge and skills required to handle gemstones sensibly and stay updated with current developments in gemmology.
- Some gemstones cannot be identified through routine inspection and testing, and in such cases, structural analysis, absence of structures, and measurable properties can help recognize or eliminate many gemstone simulants.
- With practice, experience, instincts, and a keen eye, gemmologists can identify gemstones using properties such as pleochroism, fire, refractive indices, birefringence, and more, even with the help of simple tools like a loupe.
