In 1967, a Maasai herder discovered a unique transparent blue-violet gemstone at the foot of Mount Kilimanjaro in Tanzania. He shared this discovery with a local treasure hunter named Manuel d’Souza. Overjoyed, d’Souza initially believed he had found a new sapphire deposit but instead serendipitously encountered an entirely new gemstone.

Hueb Luminus Jewelry Series Tanzanite Platinum Ring

Charles Lewis Tiffany, founder of Tiffany & Co., was a visionary innovator. Guided by the brand’s spirit of “discovery and exploration,” he and his team of gemologists passionately sought rare and extraordinary gemstones. Recognizing the immense potential of this new gem, Tiffany officially named it Tanzanite in 1968 after its country of origin, Tanzania. Under Tiffany’s stewardship, tanzanite—with its intense violet and midnight blue hues—quickly captivated global markets.

Tiffany & Co. Paper Flowers Series Tanzanite Platinum Pendant Necklace

In 1997, James Cameron’s blockbuster Titanic featured a deep blue necklace dubbed the “Heart of the Ocean” (Figure 7), worn by the protagonist Rose. While the necklace itself is fictional, its story draws inspiration from the infamous Hope Diamond. The prop used in the film was not a blue diamond but an enormous deep blue tanzanite.

Basic Properties of Tanzanite

Tanzanite’s mineral name is zoisite, a hydrous calcium aluminum silicate containing trace elements such as vanadium (V), chromium (Cr), and manganese (Mn). Key gemological properties include:

Blue/Purple Pleochroism in Heat-Treated Tanzanite; Photo by Li Qiaoqiao; Copyright © Guild Gem Laboratory

Needle-Like Inclusions in Tanzanite; Field of View: 2.96mm; Photo by Zhao Yizhi; Copyright © Guild Gem Laboratory

Rare merelaniite inclusions—a scroll-like, layered mineral rich in molybdenum, lead, and sulfur—are occasionally observed in tanzanite (Figure 10). Discovered in Tanzania’s Merelani region by Prof. John Jaszczak of Michigan Tech, merelaniite belongs to the cylindrite mineral group.

Color Origin

Blue Tanzanite: UV-Vis spectra show a narrow absorption band at 385 nm and broader absorption near 530 nm, 592 nm, and 746 nm (Figure 11).

Purple Tanzanite: UV-Vis spectra reveal absorption bands at 385 nm, 524 nm, 582 nm, 745 nm, and 799 nm (Figure 12).

Studies indicate that heat-treated blue tanzanite derives its color from V³⁺ and V⁴⁺ ions replacing aluminum in octahedral sites. Untreated brown-purple tanzanite is colored primarily by V³⁺ in the same sites (Hurlbut, 1969).

Origin

To date, the Merelani region in northern Tanzania remains the world’s sole source of tanzanite (Figure 13). This exclusivity elevates tanzanite’s rarity among gemstones.

Geographic Location of Tanzania

Simplified Geological Map of Merelani Tanzanite Deposit (Adapted from Harris et al., 2014)

Tanzanite forms through regional metamorphism and hydrothermal alteration, often coexisting with diopside, grossular garnet, graphite, and plagioclase in graphite-kyanite gneiss.

Treatments

Natural gem-quality zoisite occurs in yellow, pink, blue, green, and brown hues. Tanzanite refers specifically to blue-violet transparent zoisite. Common treatments include:

Heat Treatment:

Most natural tanzanite exhibits brown tones. Heating at 600–650°C converts V³⁺ to V⁴⁺, transforming brown hues to stable blue-violet. Heat-treated stones show reduced yellow-green pleochroism, displaying purple/blue dichroism instead. This treatment is widely accepted.

Coating:

Coatings enhance color but are non-durable, wearing off during daily wear. Identification methods include:

a. Unnatural Color: Overly vivid hues with dull, static luster and sharp color boundaries.

b. Iridescence: Rainbow-like effects on coated surfaces (Figure 16).

(Figure 16)Iridescence on Coated Tanzanite (McClure et al., 2008)

c. Edge Wear: Coating peeling at facets (Figure 17).

(Figure 17)Coating Peeling at Facets (Cooper et al., 2014)

d. Elemental Analysis: EDXRF or LA-ICP-MS detects Co, Zn, Sn, Pb, or Ti in coatings (McClure et al., 2008; Cooper et al., 2014).

Coated Tanzanite Appearance (McClure et al., 2008)

Care Guidelines

Durability: Tanzanite’s Mohs hardness (6–7) and cleavage make it prone to chipping. Handle with care during setting and wear.

Stability: Avoid sudden temperature changes, prolonged heat exposure, and contact with hydrochloric or hydrofluoric acid.

Cleaning: Use warm soapy water; avoid ultrasonic or steam cleaners.

Conclusion
Tanzanite’s journey began with a serendipitous discovery near Kilimanjaro—a phoenix rising from a wildfire’s ashes. Its vibrant hues rival any colored gemstone. In just five decades, tanzanite has blazed across global markets, ascending toward the pinnacle of gemstone fame. A rising star, its future shines brightly.