Tanzanite: Meaning, Colour, Properties & Jewellery Guide

What is Tanzanite?

Tanzanite is the blue to violet-blue variety of the mineral zoisite. Whilst zoisite itself can occur in several colours, it is the rich blue and violet tones that define tanzanite and make it so highly sought after in the jewellery world.

This gemstone was discovered relatively recently—in 1967—in the Merelani Hills of northern Tanzania, near Mount Kilimanjaro. The name "tanzanite" was chosen to reflect its exclusive Tanzanian origin, and to this day, all commercial tanzanite comes from this single location, making it geographically rarer than diamond.

Tanzanite Colour and Appearance

Tanzanite is best known for its beautiful blue and violet hues, which can range from soft periwinkle to deep sapphire-like blue, often with flashes of violet or purple depending on the light and viewing angle.

One of tanzanite's most distinctive characteristics is pleochroism—the property that causes the gemstone to display different colours when viewed from different directions. In tanzanite, you may see blue, violet, and sometimes burgundy or bronze tones depending on the crystal orientation. This optical effect adds depth and visual interest to the stone.

Because of pleochroism, skilled gem cutters carefully orient tanzanite during cutting to emphasise either the blue or violet tones, depending on the desired final appearance. This means that two tanzanites of similar quality may look quite different based on how they were cut.

Where Does Tanzanite Come From?

All commercial tanzanite originates from a small mining area near Merelani in the Manyara Region of northern Tanzania, close to the famous Mount Kilimanjaro. This single source makes tanzanite one of the rarest gemstones on Earth.

The gemstone's name was chosen to honour its country of origin, and its limited geographic availability has contributed to its desirability and value in the global jewellery market.

Natural and Heat-Treated Tanzanite

Most tanzanite found in nature initially displays brownish, greenish, or mixed tones rather than the vivid blue and violet colours associated with finished tanzanite jewellery. To bring out the desirable blue-to-violet hues, tanzanite is routinely heat-treated.

Heat treatment is a stable, permanent process that has been standard practice in the tanzanite industry since the gemstone's discovery. The treatment does not affect the durability or long-term appearance of the stone, and it is widely accepted within the jewellery trade.

Reputable jewellers will disclose heat treatment where relevant, as transparency is an important part of responsible gemstone selling. The vast majority of tanzanite jewellery available today features heat-treated stones.

Tanzanite Quality Factors

Several factors influence the quality and value of tanzanite:

Colour

Colour is the most important quality factor. The most prized tanzanites display a vivid, saturated blue or violet-blue with good depth and minimal grey or brown undertones. Stones with a balanced mix of blue and violet are particularly desirable.

Clarity

High-quality tanzanite is typically eye-clean, meaning no inclusions are visible to the naked eye. Minor inclusions may be present under magnification but should not detract from the stone's overall beauty.

Cut

A well-executed cut maximises tanzanite's colour, brilliance, and pleochroism. Cutters must carefully orient the stone to emphasise the most desirable colour direction—either blue or violet—whilst maintaining good proportions and symmetry.

Carat Weight

Tanzanite is available in a wide range of sizes. Larger stones with excellent colour and clarity command premium prices, as they are rarer and more visually impressive.

Pleochroism

The degree and balance of pleochroism can affect a tanzanite's appearance and appeal. Stones that display attractive colour shifts are often highly valued for their dynamic visual character.

Treatments

As noted, heat treatment is standard and accepted. Disclosure of any treatments is important for transparency and trust.

Overall Visual Appearance

Ultimately, the combination of colour, clarity, cut, and size determines a tanzanite's overall beauty and desirability. The best stones exhibit a harmonious balance of all these factors.

Tanzanite Durability

Tanzanite has a Mohs hardness of approximately 6 to 7, which means it is moderately hard but softer than gemstones such as sapphire (Mohs 9) or ruby (Mohs 9). This makes tanzanite more susceptible to scratching from harder materials.

In addition to moderate hardness, tanzanite has fair to poor toughness due to its cleavage—a natural tendency to break along certain planes within the crystal structure. This means tanzanite can be more vulnerable to chipping or cracking from sharp impacts compared to tougher gemstones.

Because of these characteristics, tanzanite is well suited to earrings, pendants, and necklaces, where it is less exposed to daily wear and tear. Tanzanite can also be used in rings, particularly when set in a protective setting such as a bezel or halo, and when worn with care rather than during rough or high-impact activities.

Caring for Tanzanite Jewellery

Proper care will help preserve the beauty and integrity of your tanzanite jewellery:

Cleaning

Clean tanzanite gently using warm water, a mild soap, and a soft cloth or soft brush. Rinse thoroughly and dry with a lint-free cloth.

What to Avoid

• Hard knocks or impacts that could chip or crack the stone
• Abrasive cleaners or harsh chemicals
• Sudden temperature changes, which can cause thermal shock
• Very high heat or prolonged exposure to direct sunlight
• Ultrasonic cleaners, which may cause damage due to vibration
• Steam cleaners, which can subject the stone to rapid temperature changes

Storage

Store tanzanite jewellery separately from harder gemstones such as diamonds, sapphires, or rubies to prevent scratching. A soft pouch or lined jewellery box is ideal.

Tanzanite vs Sapphire

Tanzanite and sapphire can both display beautiful blue colours, but they are very different gemstones.

Tanzanite is a variety of the mineral zoisite, whilst sapphire is a variety of corundum. Sapphire is significantly harder (Mohs 9 compared to tanzanite's 6–7) and tougher, making it more suitable for everyday wear, particularly in rings.

Tanzanite's colour often includes violet or purple flashes due to pleochroism, giving it a distinctive character that differs from the typically pure blue of fine sapphire. Tanzanite is also geographically rarer, coming from a single location in Tanzania, whereas sapphires are mined in multiple countries worldwide.

Both gemstones have their own unique appeal, and the choice between them often comes down to personal preference, intended use, and budget.