Fine jewelry is very popular not only because of its meticulous workmanship and small, exquisite specifications. Most importantly, it is because each piece of expensive jewelry is embedded with unique natural gemstones. However, there are always unscrupulous businessmen in order to earn more profit, produced fake gemstones for sale, so that many people are deceived. In order to help everyone to be able to purchase fine jewelry made of natural gemstones, this blog will introduce you to the identification methods of several common gemstones.
Ruby
Material Characteristics
Natural gemstones often contain inclusions of rutile needles, creating a unique “silky luster”. Natural rubies without any flaws or cracks are extremely rare. It is very rare to find a natural ruby of more than 3 carats on the market, so if you come across a large ruby, pay attention to it.
Appraisal Methods
Dichromaticity test: natural rubies have strong “dichromaticity”, the naked eye from different directions to see it will have two shades of red and orange-red. If there is only one color, it may be red spinel or red glass.
Stereo microscope observation: natural ruby can be seen “hexagonal growth lines” and interlaced distribution of rutile needles. Synthetic rubies, on the other hand, show curved growth lines and inclusions that are mostly bubbles or unfused powder.
Ultraviolet fluorescence test: natural rubies show a strong red fluorescence under long-wave ultraviolet light, whereas imitations with filler treatments have a weak or uneven fluorescence.
Sapphire
Material Characteristics
Sapphires belong to the corundum family, with titanium and iron as chromogenic elements, and range in color from cornflower blue to deep royal blue. Natural sapphires tend to be uneven in color and most have flat growth lines. Synthetic sapphires are uniform in color, with curved bands of growth lines, and are often seen with breadcrumb-like or bead-like bubbles in the body.
Method of Identification
Dichroic test:When the stone is turned, the natural sapphire will show blue-green-blue dichroism, while the imitation has a single color.
Stereomicroscopic observation:Parallel color bands and “fingerprint-like” liquid inclusions are common in natural sapphires. Diffusion-treated sapphires have a concentration of color layers on the surface, which is visible under the microscope as a break in the color gradient.
Emeralds
Material Characteristics
Emeralds have a rich green color due to the presence of chromium/vanadium, but natural stones almost always contain fissures and inclusions (internationally recognized as the “Garden Phenomenon”) - internal inclusions such as plant roots.
Identification Methods
Visual observation: to the naked eye, a good quality emerald has a transparent, crystalline luster. If it is translucent with interwoven fibrous mottled structures, it is generally green emerald.
Stereomicroscope observation: Colombian emeralds contain typical “three-phase inclusions” (gas + liquid + solid) in a ratio of about 3:2:1. Synthetic emeralds have inclusions in the form of nails or clouds.
Color filter test: natural emeralds appear pink under a Chelsea filter, while most imitations do not.
Opal
Material Characteristics
Natural Opal consists of 150-300nm diameter silica nanorods arranged in a regular manner, and through light diffraction can produce the color effect. Especially the top grade black opal has a flowing color like a river of stars.
Identification methods
Stereo microscope observation: natural opal color spot edge fuzzy, “lizard skin” transition. Collocation of Opal in the side of the visible glue layer, synthetic products are too regular arrangement of color spots.
Infrared spectral analysis: natural opal in the infrared spectrum under the irradiation of hydroxyl absorption peaks, while the plastic imitations do not have this feature.
Heating needle test: fake opal is usually used to achieve the effect of color change by means of injection molding. Using a heated needle to pierce the opal, the real will not be able to pierce in. Fake opals will penetrate and produce the odor of burning plastic.
Pearls
Material Characteristics
The main method of identifying pearls is to distinguish between natural pearls and cultured pearls. The difference is that the core of a natural pearl is often just a few grains of sand or parasites, or even no nucleus. The inner core of cultured pearls is artificially made larger round pearls, so the outside of the parcel layer is thinner.
Identification methods
Stereo microscope observation: natural pearl surface can be seen “stacked tile-like” growth pattern, holes can be seen at the layered structure.
Cultured pearls have obvious demarcation lines between the pearl nucleus and the pearl layer.
X-ray: natural pearls have a concentric structure, while imitation pearls (plastic/glass) are homogenous and unstratified.
Cutting method: Using a hand-carved knife or other engraving tools to cut the pearl, the natural pearl will have a regular and obvious layered structure, while the cultured pearl is cut as a solid circle.
Conclusion
There are many ways to identify gemstones, based on the identification of several common gemstones presented in this blog. It will be noted that while many gemstones can be identified as genuine or fake with the naked eye, most jewelry collectors purchase a stereo microscope for home use to ensure accuracy. A stereo microscope is a great and indispensable tool for identifying the authenticity of gemstones.