Chelsea Filter

This filter is designed to transmit only deep red and yellow-green light (best obtained under strong electric light).

Just hold the filter close to your eye and look at the stones. Multiple stones can be viewed at once.

It is helpful with identifying certain red, blue and green stones.

Chelsea filters are primarily used for spotting fakes added to colored stone parcels and mixed in jewelry, and to differentiate emerald from emerald look-alikes, it is also useful for checking aquamarine and sapphires.

With the filter emeralds usually appear distinctly red or pinkish in color, while most imitations remain green.

In rare cases certain emeralds, most notably from South Africa, may not show any pinkish color at all.

A synthetic emerald will react the same as a genuine one.