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Chelsea Filter

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(Single item price excluding VAT: £24.58)

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Pickup available from Quicktest (WD18 8JA)
Email us or call on 01923-220206 for appointment.


The original Chelsea Filter, as developed at the Chelsea College of Science and Technology in 1934.  Do not confuse this with the many copies.


Many stones appear to change colour when viewed through the filter. Originally designed for detecting synthetic emeralds, nowadays the Chelsea filter is an invaluable aid to identifying many other gemstones.

It can give an indication that you have an emeralds and aquamarines, though not a guarantee, since there is considerable variation in their chemical compositions (e.g. the amount of chromium that gives the green colour and the amount of iron that 'dampens' the effect through the filter).

It gives a very clear and spectacular result on blue stones coloured with cobalt. Since cobalt doesn't colour stones blue in nature, this is a sure-sign that you have a manmade stone (e.g. synthetic spinel) or glass.

With skill, it helps identify dozens of other stones. It's particularly useful when you have to sort large parcels of stones into 'probables' - then you have clues as to which tests to carry out next. 

Is it easy to use?

USING it is very easy indeed. Shine a light (e.g. our pen-torch) on the stone, hold the filter close to your eye, view any colour change. You don't even have to hold the stone close to the filter (only the filter has to be close to your eye) so you can examine stones in museum showcases. 

Instructions are included.

Limitations & Disclaimer

There is an instruction sheet supplied with the filter. However, in common with all gem testers, it does not provide an instant, easy and guaranteed identification of gemstones (the only 'easy' one is detecting cobalt-blue stones, which will be synthetic…or glass). 

All equipment and materials must be used in conjunction with the user's skill, knowledge and experience. Under no circumstances shall QUICKTEST be liable for direct or indirect loss sustained in connection with any item. It is your responsibility to regularly check equipment against known samples, to ensure that it is working correctly.



Ask a Question
  • Delivery in Peacehaven Brigthon uk , How many days?

    When you order you can choose the speed of service: 3 to 5 working days, or 1 to 2 working days.