Specimen at a glance
| Mineral | Zoisite (var. tanzanite) |
|---|---|
| Chemistry | Ca2Al3(SiO4)(Si2O7)O(OH) |
| Mohs hardness | 6–7 |
| Crystal system | Orthorhombic |
| You receive | The exact specimen pictured |
About this specimen
A parcel of five small rough tanzanite pieces, each displaying the mineral’s characteristic blue-violet color and strong pleochroism — the way its color shifts between blue, violet, and burgundy tones depending on the angle of light. Tanzanite is a variety of the mineral zoisite, and remarkably, it is found in only one place on Earth: the Merelani Hills at the base of Mount Kilimanjaro in Tanzania, where it was first discovered in 1967. Its striking color is caused by trace vanadium substituting into the zoisite crystal structure, and most tanzanite on the market — including material in its rough, uncut state like these pieces — is heat-treated to bring out the blue-violet hues collectors know best. Because tanzanite occurs nowhere else geologically, supplies are inherently finite, which has made it one of the more sought-after gem minerals to emerge in the last century. These five pieces are presented as natural rough, unfaceted specimens — ideal for a collector who wants to see tanzanite in its raw state, or for a lapidary hobbyist looking for cutting material to facet their own stone.
Tanzanite: the science
- Tanzanite is strongly pleochroic: turn a crystal and it shifts between blue, violet, and a brownish or burgundy tone.
- Most tanzanite rough is brownish before heat treatment. Heating removes the brown and leaves the blue-violet color.
- “Tanzanite” is a trade name introduced by Tiffany & Co. in 1968. Mineralogically it is zoisite.
Go deeper
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Questions about this piece
What is tanzanite?
Tanzanite is the blue to violet variety of the mineral zoisite. Gem-quality material comes from a single small area in the Merelani Hills of northern Tanzania.
How hard is it, and how should I care for it?
It rates 6–7 on the Mohs scale. Mohs 6–7 with one direction of perfect cleavage. Avoid knocks, ultrasonic cleaners, and sudden temperature changes. Wipe clean with a soft cloth.
Is this the exact piece I will receive?
Yes. This listing was photographed individually, and you receive the exact piece shown in the photos.
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