Can Chelsea Colour Filter Conclusively Identify Natural Emeralds | Test for Natural Emeralds

There are several tests and instruments available today to distinguish among the several types of gems and to separate the real from the fake. There are complicated tests and equipments and there are the really simple ones.

One of the easiest, compact and the most portable instrument is the Chelsea Color filter, which is almost as much in size as the loupe and fits easily into a pocket. The Chelsea Color filter is not a sure test (with the clever ways of masking treatments evolving everyday!) but it definitely is most helpful in initial screening to separate the real ones from the poseurs!

What is a Chelsea Color filter?

A Chelsea Color filter is a dichromatic filter that can transmit light only in two regions of the spectrum – red and yellow green. One can view an object only as red, green or brownish shade resulting from the combination of red and green when seen through the filter.

The Chelsea Color filter can be used to identify and separate natural emeralds from other imitations like glass, doublet emeralds or green stones like tourmalines etc.

Can it be a conclusive test for Emeralds?

When viewed from Chelsea Color filter, the Colombian and Siberian emeralds appear red (a shade of red in accordance with saturation of green in the emerald). However, the Chelsea Color filter cannot be regarded as a conclusive test for determining natural emeralds.

Here is a 2.80 carat natural treatment free Colombian emerald from Gemstoneuniverse. The pictures in Exhibit A, show the appearance of the gem through naked eye and then through the Chelsea Color filter. Notice the lovely rosy color of the gem when seen through the filter.

The Chelsea Color filter test remains unhelpful in the case of emeralds with African and Indian origin. These emeralds do not appear red when seen through this filter. Here are images of a 2.70 carat natural treatment free Zambian emerald from Gemstoneuniverse as viewed through naked eye and then through the Chelsea Color filter. The Zambian emerald in Exhibit B just presents a green-grey appearance.

Emerald Filter

In order to identify natural emeralds, it would be better to use additional instruments like the refractometer or parameters like Specific gravity rather than rely on Chelsea Color filter only. Gemologists often use a second filter called the Hanneman-Hodgekinson Synthetic Emerald Filter to further separate the synthetics.

The rule for this filter is “Red, Red, Drop dead!” Natural emeralds appearing GREEN through Hanneman-Hodgekinson filter. If a gem shows RED, it should be eliminated as a synthetic.

Selected Rings, Pendants and Talismans made available to Gemstoneuniverse.com patrons in October 2013

Gemstoneuniverse.com Table Natural Colombian Emerald Gemstone Facts

Natural Colombian Emerald of 3.92 carats

Abhijita Kulshrestha is a communications professional and held the position of Research Associate at MICA- Mudra Institute of Communications Ahmedabad before becoming certified Planetary Gem Advisor from PGA Thailand. At present she is a senior consultant at Gemstoneuniverse.com. She is a certified NLP Practitioner from NFNLP and AJP from Gemological Institute of America-GIA

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