Chelsea Color Filter September 14, 2011 · Posted In: Business Directory Share Originally created to distinguish emeralds from imitations and doublets. A doublet is two stones (one of which may be genuine) which are pasted together to make a larger stone. Only deep red and yellow-green light can pass through the filter. The filter should be held close to the eye while examining brightly lit stones. Under these conditions, emeralds will look red or pinkish. Imitations look green. (Note that this is only a rough test. Some natural emeralds may not appear pink under the Chelsea filter while some synthetics may.) Other stones that can be examined with the Chelsea color filter are ruby and sapphire. Approved by the Gemmological Association of Great Britain SKU: GM605 Price: $44.95 QTY Add to cart Click image to view enlarged