Tanzanite: The Dazzling Blue-Violet Gemstone

Tanzanite is a relatively new gemstone on the jewelry scene, first discovered in the mid-20th century. Its captivating violet-blue hue and remarkable pleochroism have quickly made it a sought-after choice for fine jewelry. Unlike many other gemstones with ancient origins, tanzanite offers a contemporary allure, appealing to those who seek something unique and distinctive.

Key Features

Tanzanite is a variety of the mineral zoisite, chemically known as calcium aluminum silicate hydroxide (Ca2Al3(SiO4)3(OH)). Its most striking feature is its color, which typically ranges from a rich, deep violet-blue to a lighter, more electric blue. This color is a result of trace amounts of vanadium within its crystal structure.

Another fascinating characteristic of tanzanite is its pleochroism. This means that a single gemstone can display different colors when viewed from different crystallographic directions. In tanzanite, this typically manifests as blue, violet, and sometimes even reddish-brown or yellowish hues. Heat treatment is commonly used to enhance the desirable blue and violet tones, often transforming the stone’s initial brownish appearance into its signature vibrant colors.

Tanzanite measures 6.5 to 7 on the Mohs scale of hardness, making it moderately durable. While suitable for everyday wear in many types of jewelry, it requires a bit more care than harder gemstones like diamonds or sapphires, particularly to protect it from sharp blows or harsh chemicals.

Origin and History

Tanzanite’s story is unique and geographically specific. It is found exclusively in a very small area near the town of Arusha in northern Tanzania, close to Mount Kilimanjaro. This limited geographic origin adds to its exclusivity and allure.

The discovery of tanzanite is attributed to Manuel de Souza, a Portuguese tailor and part-time prospector, in 1967. He stumbled upon a vibrant blue crystal in the foothills of Mount Kilimanjaro. Local Maasai people had been aware of the stones for centuries, but it was de Souza who recognized their potential value and brought them to the attention of the wider world. The gemstone was later named tanzanite by Tiffany & Co. in honor of its country of origin, Tanzania.

Types / Variations

Tanzanite is primarily known for its blue and violet colors. The most prized tanzanite exhibits a vivid, medium-dark blue with strong violet overtones, often referred to as 'VB' (Violet-Blue). Lighter blues and more purplish shades are also common.

The initial color of rough tanzanite is typically brownish. Heat treatment is crucial for developing the characteristic blue and violet hues. Stones that have not been treated, or have been treated to emphasize different color ranges, are less common and generally less valuable in the market.

How It's Made

Tanzanite is a naturally occurring gemstone formed within the earth’s crust. Its formation is linked to specific geological conditions found only in its single known deposit location in Tanzania. The mineral zoisite, in which tanzanite is found, is often embedded in metamorphic rocks.

The process that brings out the gemstone’s most desirable colors involves heat treatment. Raw tanzanite crystals, often exhibiting a brownish or grayish hue, are heated to temperatures around 500-600 degrees Celsius (930-1110 degrees Fahrenheit) for a period of time. This controlled heating process causes a charge transfer between vanadium and iron ions within the crystal lattice, resulting in the stable and attractive blue and violet colors that tanzanite is known for.

Grading & Quality Standards

Like other precious gemstones, tanzanite quality is assessed based on several factors, often summarized by the '4 Cs' – though with some tanzanite-specific nuances:

Color: This is the most important factor for tanzanite. The most desirable colors are vivid blues and violets, with saturation and hue playing key roles. Stones with a dominant, rich blue and secondary violet are highly valued. Traces of other colors, or a muddy appearance, decrease value.

Clarity: Gem-quality tanzanite should be transparent with no visible inclusions to the naked eye (eye-clean). Minor inclusions that do not detract from the stone’s beauty are acceptable, but significant flaws can impact durability and appearance.

Cut: The cut of a tanzanite significantly influences its color display and brilliance. Gem cutters often employ cuts that maximize the blue and violet tones, taking pleochroism into account. Shapes like oval and cushion cuts are popular, but custom cuts are also used to enhance specific color characteristics.

Carat Weight: Larger tanzanite stones are rarer and thus command higher prices per carat. The perceived color can also change with size; larger stones often display more intense and saturated colors.

Origin: While not a formal grading factor like the 4 Cs, the knowledge that a tanzanite is from the sole mining region in Tanzania can add to its perceived value and authenticity.

Buying Guide

When purchasing tanzanite, consider the following:

Color: Look for a vibrant blue or violet color that appeals to you. Consider the intensity and saturation. Remember that heat treatment is standard and not a negative factor.

Clarity: Aim for eye-clean stones. Hold the gemstone under good light and look for any distracting flaws or inclusions.

Cut: A well-cut tanzanite will sparkle and show off its best colors. Examine the symmetry and polish. Avoid stones that appear too dark or too pale due to poor cutting.

Durability: Understand that tanzanite is less durable than diamonds or sapphires. If you plan to wear the jewelry daily, consider protective settings like bezels for rings.

Certification: Reputable jewelers will provide certification from a recognized gemological laboratory, detailing the stone’s characteristics. This ensures authenticity and quality.

Source: Purchase from trusted and reputable jewelers to ensure you are getting genuine tanzanite of good quality. Be wary of unusually low prices, which could indicate synthetic stones or lower-quality material.

Price Range & Value Factors

Tanzanite prices vary significantly based on the factors mentioned above, particularly color, clarity, and size. Generally, tanzanite is more affordable than traditional precious stones like sapphires, diamonds, or emeralds.

Color: The most intense and desirable blue-violet hues command the highest prices. Stones leaning too heavily towards purple or lacking saturation will be less expensive.

Clarity: Eye-clean stones are more valuable. Visible inclusions can reduce the price considerably.

Carat Weight: Price per carat increases exponentially with size. A 5-carat tanzanite will cost significantly more per carat than a 1-carat stone of similar quality.

Cut: A skillfully cut stone that maximizes color and brilliance will be more valuable than one that is poorly cut.

Treatment: While heat treatment is standard, disclosure of any treatments is expected. Untreated stones showing desirable color are exceptionally rare and may command a premium, but this is uncommon in the market.

Prices can range from under $100 per carat for smaller, less intense stones to well over $1,000 per carat for exceptional, large, and vividly colored specimens. Most fine quality tanzanite falls somewhere in the middle of this range.

Care and Maintenance

Proper care is essential to maintain the beauty and integrity of tanzanite jewelry:

• Avoid Harsh Conditions: Due to its Mohs hardness of 6.5-7, tanzanite can be scratched or chipped. Avoid wearing tanzanite jewelry during strenuous activities, sports, or when exposed to harsh chemicals (like cleaning agents or perfumes).
• Cleaning: The best way to clean tanzanite is with warm, soapy water and a soft brush. Gently scrub the stone and its setting, then rinse thoroughly and dry with a soft, lint-free cloth. Avoid ultrasonic cleaners and steam cleaners, as the rapid temperature changes and vibrations can cause damage.
• Storage: Store tanzanite jewelry separately from other gemstones and jewelry to prevent scratches. Use a soft pouch or a lined jewelry box.
• Professional Inspection: Have your tanzanite jewelry inspected by a professional jeweler periodically to check for any loose stones or damage to the setting.

Pros and Cons

Pros:

• Stunning and unique blue-violet color
• Pleochroism offers visual interest
• More affordable than many traditional precious gemstones
• Limited geographic origin adds to its appeal
• Modern and contemporary choice for jewelry

Cons:

• Moderate durability (Mohs 6.5-7) makes it susceptible to scratches and chips
• Requires careful handling and specific cleaning methods
• Limited supply due to single known mining location
• Color is typically achieved through heat treatment

Famous Examples

While tanzanite doesn’t have the centuries-old lineage of famous gems like the Hope Diamond, several notable pieces have showcased its beauty. One significant tanzanite is the 'Queen of Kilimanjaro', a massive 242-carat cushion-cut tanzanite, renowned for its exceptional color and size. Many high-end jewelry designers feature tanzanite in their collections, creating bespoke pieces for discerning clients.

Common Misconceptions

Misconception 1: Tanzanite is a synthetic stone or imitation.
Reality: Tanzanite is a natural gemstone, a variety of zoisite. Its rarity and relatively recent discovery sometimes lead to confusion, but it is a genuine precious gemstone.

Misconception 2: The blue color of tanzanite is natural and permanent.
Reality: While tanzanite is naturally blue and violet, the intensity and desirable hue are typically enhanced through heat treatment. This treatment is stable and standard in the industry.

Misconception 3: Tanzanite is as durable as a diamond.
Reality: Tanzanite has a Mohs hardness of 6.5-7, making it significantly less hard and more prone to scratching and chipping than diamonds (Mohs 10) or sapphires (Mohs 9).

Related Terms

• Zoisite
• Pleochroism
• Heat Treatment
• Gemstone Durability
• Tanzania
• Blue Gemstones
• Violet Gemstones
• Semi-Precious Gemstones

FAQs

Q1: Is tanzanite a good investment?
A1: While tanzanite can hold its value, it's generally considered more of a beautiful gemstone for personal enjoyment than a traditional investment gem like diamonds or gold. Its value is tied to market demand and the gemstone’s inherent beauty and rarity.

Q2: What does 'tricolor' tanzanite mean?
A2: 'Tricolor' refers to the pleochroic nature of tanzanite, where it can display three distinct colors (typically blue, violet, and reddish-brown or yellow) when viewed from different angles. Most desirable tanzanite is heat-treated to emphasize the blue and violet tones, minimizing the other colors.

Q3: Can tanzanite be worn every day?
A3: It can be worn daily with care, especially if set in protective mountings like bezels. However, it's advisable to remove tanzanite jewelry during activities where it might be exposed to impact, harsh chemicals, or extreme temperatures.

Q4: How can I tell if tanzanite is real?
A4: Purchase from reputable jewelers who provide certification. A trained gemologist can identify tanzanite by its color, pleochroism, refractive index, and specific gravity. Beware of prices that seem too good to be true.