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A variety of Zoisite

A gem variety of zoisite with a blue to blue-violet colour.

Note that a significant percentage of tanzanite crystals on the market have been heat-treated (400-500°C) to produce or enhance this colour, many are originally brown or pale grey (Hurlbut 1969; see photo to the right). A red tint seen looking down the c-axis is a good indication that the crystal colouration is natural. Note also that tanzanion is used as a synthetic simulant for tanzanite.
Natural and heat-treated tanzanite is strongly pleochroic (Hurlbut 1969). The photo to the right shows a single crystal viewed from different directions.

First reported from the Merelani Hills (Mererani), Tanzania.

Visit for gemological information about Tanzanite.

Classification of Tanzanite

Chemical Properties of Tanzanite

Elements listed in formula:

Other Names for Tanzanite

Name in Other Languages:
Norwegian (Bokmål):Tanzanitt

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Tanzanite

Reference List:
Hurlbut, C.S., Jr. (1969) Gem zoisite from Tanzania. American Mineralogist: 54: 702-709.

Internet Links for Tanzanite URL:
Please feel free to link to this page.
The following Tanzanite specimens are currently listed for sale on

Localities for Tanzanite

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
(TL) indicates type locality for a valid mineral species. (FRL) indicates first recorded locality for everything else. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
No reference listed
  • Manyara Region
    • Simanjiro District
      • Lelatema Mts
        • Merelani Hills (Mererani)
Wilson, W.E., Saul, J.M. Pardieu, V. & Hughes R.W. (2009): Famous Mineral Localities. The Merelani Tanzanite Mines, Lelatema Mountains, Arusha Region, Tanzania. Mineralogical Record, 40: 347-408.
Wilson, W.E., Saul, J.M. Pardieu, V. & Hughes R.W. (2009): Famous Mineral Localities. The Merelani Tanzanite Mines, Lelatema Mountains, Arusha Region, Tanzania. Mineralogical Record, 40: 347-408.
Min Rec (2009) 40:347-408
Olivier, Bernard (2008): The geology and petrology of the Merelani tanzanite deposit, NE Tanzania. Doctoral thesis, University of Stellenbosch, South Africa.
Andy Seibel
Natural HistoryMuseum of Los Angeles Co.specimen catalogue No. 41249.
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