• Location: Merelani Hills, Tanzania
• Weight (with base): 10.7g
• Crystal Size: 1.1 x 0.5 x 0.2 cm
• DETAILED DESCRIPTION

Tanzanite – a rare mineral that changes color depending on the viewing angle

Tanzanite is a rare mineral with a distinctive bluish-violet color, found in only one location in the world: the Merelani Hills, Tanzania. It is a variety of the mineral zoisite, prized for its unique coloration and strong pleochroism, which is the ability to display different hues depending on the viewing angle. The color of tanzanite is mainly due to the presence of the trace element vanadium, which influences the absorption and reflection of light within the crystal.

Discovery of Tanzanite

Tanzanite was discovered relatively recently, in 1967, in northern Tanzania. According to popular accounts, it was found after natural fires highlighted and intensified its coloration. Due to its limited geographical distribution and recent discovery, it is considered a modern and exceptionally rare mineral.

Rough Tanzanite and its Coloration

Rough tanzanite fascinates with its natural structure, crystal form, and play of colors. In its unheated state, it is generally trichroic, meaning it can display different color shades—mainly blue, violet, and delicate wine-red tones—depending on the angle from which it is viewed.

Heat Treatment of Tanzanite

An interesting fact is that most tanzanite on the market has undergone heat treatment to enhance its characteristic coloration. During heating, some chromatic components are reduced, and the stone becomes predominantly dichroic, primarily displaying two main colors: blue and violet. This process is common, stable, and does not alter the fundamental nature of the mineral.

Formation

Tanzanite formed approximately 500–600 million years ago under very specific geological conditions, linked to the movement of tectonic plates in what is now northern Tanzania. During the collision and deformation of the Earth's crust, intense pressures and high temperatures transformed original rocks rich in calcium and aluminum. In the presence of vanadium, zoisite formed in its bluish-violet variety known as tanzanite.

These unique geological processes occurred exclusively in a narrow belt of the Merelani Hills, which is why tanzanite is found only in this location and is considered one of the rarest minerals in the world.

Rough tanzanite specimens are particularly sought after for their authenticity and natural beauty, which stands out without any intervention or treatment. They are ideal for mineral enthusiasts, collectors, and anyone who appreciates the uniqueness of natural crystals.

Origin: Merelani Hills, Tanzania.