Tanzanite Gemstone: How to Identify a Genuine Stone

If you are an avid gem enthusiast, you must be aware that tanzanite is one of those rare finds that makes collectors' hearts skip a beat. The reason for being so rare is that it is found only in the foothills of Mount Kilimanjaro in Tanzania. This stunning blue-violet gemstone is actually rarer than diamonds. Expert geologists estimate it's about 1,000 times scarcer. 

And here's the catch. With rarity comes fakes, lots of them. So whether you're buying your first tanzanite ring, your wedding band or adding this December birthstone to your collection, knowing how to spot a genuine stone can save you from expensive mistakes. Let's walk through the practical ways to identify real tanzanite without needing a gemology degree.

The Color-Changing Magic: Trichroism

One of the first things you can look for in a genuine tanzanite gemstone is its ability to change colors depending on the light and angle of observation. This is called trichroism, and it's your first indicator of a genuine gemstone.

Angle: Hold the gemstone and turn it around while under bright lighting. A real piece of tanzanite gemstone will change colors between blue, violet, and even burgundy or reddish hues depending on the angle of observation. If your gemstone refuses to change colors regardless of the angle, then it's likely a fake.

Light: Another way to test it is through light. Examine the stone under varying light sources. Under bright lighting, such as daylight or fluorescent lighting, tanzanite will always have a blue undertone with purple overtones. Switch to warm lighting, such as incandescent lighting (like a regular lamp), and see how it changes. Now the purple is more prominent, sometimes with pink or red flashes. Counterfeit stones won't vary with lighting.

The Dichroscope Test: Double Vision

If you want to get a bit more technical, a dichroscope is your best friend. It is more like a scientific test. It's a small instrument (you can find one online for a few bucks) that has two viewing holes.

When you view tanzanite through the dichroscope, you'll see two different colors in the two holes. One might display blue, while the other displays violet. This is because tanzanite is a doubly refractive stone, which means that light passes through it in two different directions.

Most forgeries, such as cubic zirconia, synthetic spinel, and colored glass, are singly refractive. This means that when you view them through a dichroscope, you'll see the same color in both holes. That's a dead end.

Inclusions: The Beautiful Imperfections

Here's something that'll catch people off guard. Flawless are often fakes. In fact, the only way to be very sure when it comes to tanzanite is to look for its flaws and inclusions. Picture-perfect stones and clarity could mean they are fake.

Take out a 10x jeweler's loupe or even a magnifying glass and take a closer look at the gem. Natural tanzanite takes millions of years to form in high heat and pressure. Such an ordeal leaves its mark in the form of small inclusions, tiny scratches, or internal structures.

If your gem is completely flawless, with no inclusions visible under magnification, you could be looking at forsterite (common tanzanite imitation) or another lab-created gemstone. While some high-quality tanzanite may be "eye-clean" (flawless to the naked eye), there should still be something visible under magnification.

The Sparkle Factor: Refractive Index

Natural tanzanite has a high refractive index, which essentially means it's very good at bending light. This is what gives it that amazing sparkle and brilliance that draws you in from across the room.

Compare your gem to a genuine known gemstone, or even just look at it in bright lighting. Imitation tanzanite will often appear dull or even lifeless in comparison. That flat, shallow sparkle is a red flag that you're looking at something that's trying too hard to be what it's not.

Size and Color Intensity

The best tip on tanzanite value and quality is that the color deepens as the stone increases in size. In smaller tanzanite stones weighing less than five carats, the color tends to be lighter and less saturated. If a person is attempting to sell you a small stone with an extremely deep and saturated blue-violet color, don't get conned; that's highly unusual for natural tanzanite.

The most prized tanzanite will have a rich, vivid blue, purplish blue, or violetish blue hue. Lighter colors are still natural (and more budget-friendly). However, if the color is extremely dark and saturated in a small stone, it could be treated in a way that goes beyond the standard heating process, or it could be an entirely different gem altogether.

Heat Treatment: The Industry Standard

Almost all tanzanite on the market has been heat-treated, and this is perfectly normal and accepted. In its natural form, tanzanite is actually brown. Heat treatment at 600 degrees Celsius gives it the renowned blue-violet color.

This is not considered "faking" or deceptive in any way. It's standard industry practice and should be openly disclosed by reputed dealers. Only a small fraction of tanzanite comes out of the ground naturally blue, and these stones command premium prices from collectors who specifically look for untreated specimens of gemstones.

The key is to understand what you're getting. Ask if the stone has been heat-treated (the answer will inevitably be yes), and ensure that it is taken into account in the price.

Make the Purchase from a Reliable Source

Listen, all these tests are great, but if you're shelling out big bucks for tanzanite, get it certified from an entrusted gem lab. Period. Take the professional route when in doubt.

If you are making your purchase from a reputed jeweler, like GemsNY, it will provide certification from trusted gemological labs such as GIA (Gemological Institute of America), IGI (International Gemological Institute), or AGL (American Gemological Laboratories). These reports will not only confirm that your stone is authentic tanzanite, but also disclose any treatments and grading information for color, clarity, and other factors.

Common Tanzanite Imitations

The following are the most common substitutes for tanzanite. You should know them while hunting for the real ones. 

Synthetic Forsterite: Produced in Russia since the late 90s, this is very similar to lower-quality tanzanite but lacks the trichroic properties and strength.

Cubic Zirconia: Can be dyed to resemble tanzanite, but is singly refractive and does not exhibit color shifts with changes in lighting.

Synthetic Spinel: Another blue-violet substitute that is singly refractive but lacks the defining features of tanzanite.

Colored Glass: The most economical substitute. Usually easy to spot with a jeweler's loupe, very clear with air pockets and no inclusions.

Buy Certified Tanzanite Gemstone

Companies such as GemsNY, which have been in the industry for many years, understand the importance of certification and honesty. By going through GemsNY reviews from satisfied customers, you will get to know how they handle customer concerns and maintain the legacy of trust for decades. It will give you a sense of confidence that you are putting your money at the right place. 

If you are planning to buy loose gemstones from a new or unknown source, ask for certification. If they cannot or will not provide it, do not purchase. It's that simple.

Final Words

Tanzanite is truly a special gem and is already becoming rare. Besides being a popular choice in custom engagement rings, it is also becoming a prominent part of three-stone rings. Geologists and industry experts believe that this rare gemstone will become extinct in the next two decades or so, which only adds to its allure and value. This rarity not only means a lack of availability but also allows its counterfeits to continue to pour into the market.

However, with knowledge of trichroism, double refraction, and understanding of natural inclusions, and of course, proper certification, you can buy this beauty with confidence. So, no matter whether you are gifting this stone to a December-born or simply buying it for its incredible blue-violet hue, make sure you are adhering to the above-mentioned points in the article. Your future self will thank you. Subscribe to GemsNY Press to stay updated about the latest news in the gem world.