How do I Heat a Tanzanite?

Written by megan shoop
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How do I Heat a Tanzanite?
Tanzanite stones will turn a deep, brilliant blue when heated. (tanzanite image by Julianna Olah from

Tanzanite features a brilliant, deep blue colour that takes well to faceting and refracts light in a rainbow of lighter blues. However, freshly mined tanzanite sports a rather dull brown colour. Tanzanite must be heat-treated after mining to achieve its signature blue glow. Before heating, tanzanite is actually a variety of zoisite. As the stone heats, the inclusions, or structure, of the stone becomes denser, resulting in tanzanite's typical colour. Heating tanzanite at home is challenging, but can be done with the right equipment.

Skill level:

Things you need

  • Unheated tanzanite stones
  • Kiln tray
  • Ceramic kiln

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  1. 1

    Place your pieces of unheated tanzanite on a kiln tray, spacing them about 1 inch apart. Smaller tanzanite pieces are easier to heat through than larger ones, so none of your tanzanite stones should be much larger than a silver dollar. Make sure the stones are about 1 inch away from the edges of the tray.

  2. 2

    Place the tray in the kiln, centring it as much as possible. If you have a large kiln, place the tray in the centre of the centre shelf. If your kiln is smaller, place it as close to the centre of the single shelf as possible.

  3. 3

    Set your kiln temperature to about 454 degrees Celsius. Once your kiln reaches this temperature, turn the temperature up about -12.2 degrees C every 15 minutes or so until you reach about 498 degrees C.

  4. 4

    Heat the tanzanite at 499 degrees Cor about 1 hour. You can check on it briefly to see how the colour is changing. If it has not changed, stick it back in for another 2 hours. Continue this way for about 4 hours, then check on the tanzanite every hour for two hours, then every 30 minutes for two hours. Your tanzanite should reach its optimum colour somewhere in this time frame.

  5. 5

    Remove your tanzanite from the kiln and let it cool for about 24 to 48 hours in a dark, cool place. Your tanzanite is now ready for shaping and jewellery.

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