Hold the filter an inch or two from the eye. Light the stone with a strong incandescent light bulb or torch, not LED. The stone may appear to change colour. The filter must be held near to the eye but there is no need to hold the filter close to the stone, even items in showcases can be examined providing they are lit by strong lights.
Chelsea Filters were also used to help separate aquamarine and natural zircon from synthetic flame-fusion spinel (used extensively in “birthstone” jewelry), as both of the former absorb the red portion of the spectrum and the synthetic spinel did not.
Some gemstones appear to change colour when viewed through the Chelsea Colour Filter. This colour change helps identify many gemstones, distinguishing ruby from paste; distinguishing garnet (though not all garnets) emerald and aquamarine from paste.
The Chelsea Filter also distinguishes many manmade stone such as cobalt-blue glass and blue synthetic spinel from natural blue stones.
- 1 x Chelsea Filter
- 1 x Leather Case
- 1 x Box