Tanzanite

Rare minerals that change color depending on the angle of view

Tanzanite is a rare mineral of distinctive blue to violet color, found only in a single location in the world – in the Merelani Hills area of Tanzania. It is a variety of the mineral zoisite, valued for its unique coloration and strong pleochroism, meaning its ability to change shades depending on the angle of view. The color of tanzanite is primarily caused by the presence of the trace element vanadium, which influences the absorption and reflection of light within the crystal.

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Discovery of tanzanite

Tanzanite was discovered relatively recently, in 1967, in northern Tanzania. According to the most widely known accounts, it was found after natural fires that exposed and enhanced its coloration. Due to its limited occurrence and relatively recent discovery, it is considered both a modern and exceptionally rare mineral.

Raw tanzanite and its coloration

Raw tanzanite captivates with its natural structure, crystal form, and play of colors. In its unheated state, it is typically trichroic, meaning it can display different color shades – most commonly blue, violet, and subtle wine-red tones – depending on the viewing angle.

Heat treatment of tanzanite

An interesting fact is that most tanzanites on the market have undergone heat treatment, which enhances their characteristic coloration. During heating, certain color components are reduced, and the stone becomes predominantly dichroic, displaying mainly two primary colors – blue and violet. This process is common and stable, and it does not alter the fundamental nature of the mineral.

Formation

Tanzanite formed under very specific geological conditions approximately 500–600 million years ago in connection with the movement of tectonic plates in what is now northern Tanzania. During the collision and deformation of the Earth's crust, intense pressure and high temperatures transformed original rocks rich in calcium and aluminum. In the presence of the trace element vanadium, the mineral zoisite formed in its blue-violet variety known as tanzanite. These unique geological processes occurred only within a narrow belt of the Merelani Hills area, which explains why tanzanite is found only in a single location worldwide and is considered an exceptionally rare mineral.

Raw tanzanite specimens are 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.