What do gemstone collectors, rock hounding enthusiasts, and geologists have in common?
A love of rocks! Also, what drives each respective role is the process of discovery.
An ongoing effort to become familiar with various rocks, stones, and minerals, enough to recognize what’s significant about them.
This article will help contribute to this process by laying out a general comparison between two distinct gemstones – Alexandrite and Tanzanite.
We’ll look at traits unique to each stone, how the stones are similar to one another, and what sets them apart.
Lastly, we’ll talk about why Alexandrite and Tanzanite may reasonably be confused as the same rock.
Alexandrite vs Tanzanite: Explained
What is Alexandrite?
Alexandrite was first discovered in the year 1830.
A blue-green stone by day and purple-red in incandescent lighting, Alexandrite was found in the Ural Mountains of Russia.
The color changing characteristic of Alexandrite is due to the mineral chrysoberyl that is present.
A rare and valuable gemstone, today’s Alexandrite is found in Sri Lanka, Brazil, and East Africa.
Alexandrite is most commonly found as a byproduct discovered in emerald mines, uncovered incidentally while looking for other stones.
It is of no surprise that Alexandrite is quite rare.
Alexandrite is also durable and has a hardness level of 8.5 on the Mohs scale, a scale numbered 1 – 10 used to rate the hardness of minerals, where 10 is the most durable.
Trace minerals including chromium, titanium, and iron are found in Alexandrite and it’s these minerals which give the stone its brilliant greenish red vibrance.
How to know Alexandrite is real
The best way to know if an Alexandrite stone is the real deal is to take it to a jeweler.
However, there are ways to identify if you have an authentic stone if a jeweler is not an option.
Alexandrite changes color depending on the lighting.
The stone will appear emerald-green in color when viewed under bright light and reddish-purple when viewed under dim light.
The contrast between each color shifting is very noticeable if the stone is real.
Fake or synthetic Alexandrite stones are most common, recognizable by their color changing from gray-blue to pink, instead.
What is Tanzanite?
Belonging to the mineral group epidote, Tanzanite is a brilliant stone found in Tanzania.
Tanzanite stone is mined near an incredibly small hillside area of the country, making this stone incredibly rare.
Known for its pleochroism color characteristics, Tanzanite usually appears blue, violet, or burgundy.
Pleochroism, or a gemstone with “more colors”, is primarily what makes Tanzanite so alluring.
The color variations that characteristically define Tanzanite appear different depending on the angle at which the stone is observed, due to light reflecting different cuts in the stone.
Additionally, colors may appear to change when viewed under different types of light.
In its pre-polished state, Tanzanite has a reddish-brown tint and may appear clear.
To bring out the rich blue-violet colors, the stone must be treated with heat to remove the burgundy layer.
Treating a Tanzanite stone removes the rough reddish surface color and uncovers a more pronounced blue-violet hue.
The heat treatment process results in a dichroic stone reflecting only violet and blue colored shades of light.
There is no single or standard method of grading the value of Tanzanite.
However, color and clarity are two factors dividing the market.
A Tanzanite stone is generally worth less if inclusions are present.
Inclusions are minerals trapped beneath the surface of the stone that are visible from the outside.
Additionally, a well-cut Tanzanite stone is one that looks most pristine with respect to color brilliance and overall aesthetics.
Cutting Tanzanite one way alters how light is reflected and therefore changes the stone’s resulting colors.
How to know Tanzanite is real
All genuine Tanzanite is natural Tanzanite because the stone has not successfully been synthesized artificially.
Although Tanzanite fakes indeed exist.
Because Tanzanite stones are highly valuable, in demand, and rare, there is a high incentive to sell counterfeits.
Fake Tanzanite is commonly made using cubic zirconia, spinel, synthetic crystalline material, or colorful glass.
However, when viewed under a dichroscope, only genuine Tanzanite appears doubly refractive – a condition where a single light wave entering a mineral becomes split into two distinct rays of light that move out in two separate directions.
Similarities and Differences Between Alexandrite and Tanzanite
Both Alexandrite and Tanzanite are rare and valuable gemstones with variable color profiles. Both stones display brilliant colors and are relatively durable.
Alexandrite and Tanzanite are highly sought after gemstones for their aesthetics, quality, and rare value.
The most apparent similarity between Alexandrite and Tanzanite stones is in the way they both appear to change and adopt different colors depending on how they are viewed.
However, a notable difference between Alexandrite and Tanzanite is in how each reflects light – that is what’s responsible for each stone’s unique color quality.
While Alexandrite changes its hue from green to red when viewed under bright or dim lighting, Tanzanite looks bluish-violet depending on the way it’s cut.
In other words, while each gemstone displays unique and defining shades and color variations, Alexandrite changes depending on the intensity of light used to view it.
On the contrary, Tanzanite stones appear to be different colors depending on the angle of the stone’s cuts, which the light reflects.
Moreover, Tanzanite is less durable than Alexandrite, with a hardness rating of 6.5 compared to Alexandrite’s 8.5 hardness rating.
Consequently, Tanzanite jewelry may be worn every day but requires greater care to keep from chipping, more so than pieces made with Alexandrite gemstones.
Lastly, Tanzanite stones are only found in Tanzania, making mining efforts exclusive to only one area of the world and therefore less accessible than many other stones.
Similarly, while Alexandrite stones may be discovered in several locations around different countries, they are typically found as a byproduct of mining for Emeralds and not as a result of intentional or commercial mining efforts.
To put it in perspective, this is how exceptionally rare Alexandrite gemstones are.
Approximately one Alexandrite stone is uncovered with every batch of about a hundred or so Emeralds.
Whether you are a geologist, gemologist, or rare stone collecting connoisseur, the story behind each stone is found in the details of its excavation, treatment, and value – details vital to each purpose.
An eye for detail, which is necessary for examining rare stones, is only helpful if you know what details you are looking for and why they are significant.
This article can serve as a reference to kickstart further inquiry into two of the rarest gemstones in the world.
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