Tanzanite Zoisite

Tanzanite is a rare and precious gemstone celebrated for its vivid blue-violet hues and remarkable colour-changing properties. Due to its pleochroism, tanzanite can appear blue or violet depending on the viewing angle and lighting. With its exceptional vibrance and rarity, tanzanite has become a sought-after choice for gemstone collectors and jewellery enthusiasts.

Chemical Composition: Calcium Aluminium Silicate (Ca₂Al₃(SiO₄)₃(OH))

Crystal System: Orthorhombic

Refractive Index: 1.69 to 1.70

Specific Gravity: 3.15 to 3.38

Double Refraction: 0.006 to 0.013

Mohs Hardness: 6.5

Lustre: Vitreous

Tanzanite is a rare single origin gemstone, found in the Merelani Hills of Tanzania, near Mount Kilimanjaro. This small mining area, just a few kilometres long, is the only known source of natural tanzanite. Its unique geological formation makes it an incredibly rare gemstone, often considered 1,000 times rarer than diamonds. Due to its single-source origin, tanzanite's supply is finite, and its long-term availability remains uncertain.

Tanzanite can be used in an engagement ring but requires extra care as it softer than sapphires and diamonds, making it more susceptible to scratches and impact damage. If used in an engagement ring, it is best set in a protective design, such as a bezel or halo setting, to minimise exposure. Tanzanite's stunning colour and rarity make it a luxurious and unique choice, but ideally, it is best suited for occasional wear rather than everyday exposure.

Tanzanite's value is primarily determined by colour, clarity and size. The most prized tanzanites display a rich, intense blue-violet hue with strong pleochroism. Deeper blues are generally more valuable than lighter purple tones, as they resemble the finest sapphires. Clarity also plays a role; eye-clean tanzanites with minimal inclusions command higher prices. Large, high-quality tanzanites over 5 carats are especially rare and significantly more valuable.

Nearly all tanzanite on the market is heat-treated to enhance its blue-violet colour by removing brownish undertones. This process is stable and permanent, making it an accepted industry practice. You can generally tell if tanzanite is unheated because it may display green and purple or be a silvery hue, sometimes referred to as 'mermaid tanzanite'. Unlike many other gemstones, tanzanite is not subjected to additional treatments such as irradiation or surface coatings. Naturally, vivid tanzanites that do not require heat treatment are extraordinarily rare and highly collectible.

The rarest variety of tanzanite is natural green zoisite, sometimes called "Green Tanzanite." Unlike the classic blue-violet tanzanite, green zoisite features a mix of green, yellow, and bronze hues caused by the presence of vanadium a colouring element within the crystalline structure of the gemstone. It is much less common than traditional tanzanite and is left untreated. Collectors prize these unique green specimens for their unusual colouring and rarity.

Tanzanite is the birthstone for December, alongside turquoise and zircon. It is often chosen for its rich, wintry blue tones, making it a fitting gemstone for those born this month. Introduced as an official birthstone in 2002, tanzanite is the newest addition to the modern birthstone list.

Tanzanite is a gemstone of transformation, spiritual enlightenment, and emotional healing. It is associated with intuition, clarity, and inner strength. Many cultures regard tanzanite as a gem that enhances communication and higher consciousness, making it a popular choice for meditation and self-discovery. Its deep blue shades symbolise wisdom and truth, while the violet tones are linked to creativity and inspiration.

Natural tanzanite is often eye-clean, but under magnification, it may show needle-like inclusions or subtle growth patterns. Synthetic tanzanite does not exist, but imitations such as blue-violet glass, synthetic spinel, and cubic zirconia are sometimes sold under misleading names. To ensure authenticity, always buy from a trusted jeweller and consider a gemological certificate for verification.