How to tell if tanzanite is real or not

Written by karla h
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How to tell if tanzanite is real or not
Tanzanite is used in a numerous types of jewelry. (Getty Images)

Named for its African country of origin, tanzanite is a blue stone used as a substitute for sapphire. Unlike the sapphire, tanzanites are a three-coloured gemstone. They contain three different shades of reds, purples, and blues that are visible to the naked eye. Synthetic forsterite and blue-violet glass are both sold as tanzanite imitations. Besides inspection from a jeweller, there are steps you can take to determine the authenticity of your tanzanite.

Skill level:

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  1. 1

    Place stone on white surface. If the stone is mounted, place light below.

  2. 2

    Hold filter around 36 cm (14 inches) from your eye, right over the stone.

  3. 3

    Move filter from side to side, using the strip as a guide. View the stone from several different angles while moving the filter to ensure accurate results.

  4. 4

    Compare colours seen with enclosed instruction chart. Imitation tanzanite such as fosterite will show a green colour through the filter. Authentic tanzanite will appear a pinkish-orange colour through the filter.

Tips and warnings

  • There are test kits that include both a filter and dichroscope, many also have a detailed chart with colour descriptions.
  • Filters may also be called "Hanneman" filter.
  • Using fluorescent or sunlight will cause incorrect readings with a filter.
  • Stones that have been set with a dark solid backing may be harder to test using a dichroscope or filter.

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