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Tanzanite
(The One & Only)

Tanzania Deposits, Tanzanite
Tanzanite Crystal
World Map of Gemstones.png

TANZANITE

Tanzania (Southeast Africa)

Gemstone Marketing Trade Term: "Tanzanite"

 

Geography:   Contact Metamorphic (calcium enriched shales/ schists)

Crystal Structure:  Orthorhombic 

Composition:  Zoisite (Ca2Al3(SiO4)3(OH)) + Vanadium

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When heated, the vanadium goes through a redox reaction creating the unique Indigo (blue/ violet) color in Zoisite.

Mt Kilimanjaro, Tanzania

Mt Kilimanjaro, Northern Tanzania:  The claims are just 50mi southwest of Mt Kilimanjaro in the Merelani Area.

There is no need to identify the origin of a Tanzanite.  It comes from one mine in the Merelani area of Tanzania.  

 

Again, this area is the one and only source on earth.

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With its pleochroism (three colors) that radiate violet, blue, and indigo colors, it really has no competitor.  A fine Tanzanite is most certainly one gemstone to invest in at the right price.​

Tanzanite Block C and D Mine Tunnels.jpg

Large Tanzanite ramp mining tunnels extending from shafts

Tanzanite One is separated by mining blocks, like districts within the mine.  The production of Tanzanite is not consistent.  Most of the finer material has been said to come from Block D, in one concentrated area.

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Blocks have a main shaft that leads to large ramp mining tunnels.  Advanced mining techniques are used.  The host rocks for tanzanite are mainly graphitic gneisses, dolomitic marbles, and schists.  Much of the material in the mine has been extracted.  They are basically "scrapping the bottom of the barrel."  ​​

Inclusions & Clarity Characteristics​

Since there is only one geographic location for Tanzanite, origin identification is not really necessary.  In addition, Tanzanite gems are typically eye-clean.  However, liquid inclusions are quite familiar in this mineral.

 

Tanzanite is almost always heat treated in order to change its color.  After the process, it becomes a rich, vivid violet and blue color.  ​

unheated tanzanite

Natural Tanzanite before the heat treatment process to improve color

Fine Tanzanite Pave Diamond Ring
liquid inclusions in Tanzanite

Jagged, misshapen liquid inclusions

Approximately 90-95% of all Tanzanite is estimated as having been heat treated.  Untreated, tanzanite is typically yellowish to reddish brown, green, or lavender.  High temperature exposure to natural sources are expected to be the reason for Natural Blue Tanzanite.

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