Gemax Chelsea Filter

Correct Chromium Filter. Stable & accurate results !!!

INTRODUCTION

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. As with all gem testers, care must be taken since nature does not make gemstones to standard formulae and variations exist.

HOW TO USE A CHELSEA FILTER

Hold the filter an inch or two from the eye. Shine a light on the stone with a strong light bulb or torch. 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.

HOW IT WORKS

White light is made up of all the colours of the rainbow (a spectrum): red, yellow, green, blue. Colours are known, technically, as wavelengths of light. A gemstone will absorb some wavelengths and leave the others free to reach the eye. It is these which mingle to give the appearance of colour. Emerald absorbs virtually all the yellow/green wavelengths; the Chelsea Colour Filter filters out all but the yellow/green and deep red wavelengths. Since the yellow/green has already been absorbed by the emerald, only red is left to pass through the filter.

THE IDENTIFICATION OF EMERALD

Most emerald will appear to change from green to red when viewed though the filter, paste and other stones remain green/dark though the filter. The brightness of the red depends on the amount of chromium in the stone. There is no chromium in most green stones; in natural emeralds chromium is present in small quantities; in synthetic emeralds chromium is present in large quantities. Therefore paste, peridot, sapphire etc. appear green/dark through the filter; most natural emeralds will appear red (from dull red to bright red) through the filter; synthetic emeralds will often appear a brilliant glowing traffic light red. HOWEVER, some modern synthetic emeralds appear only a dull red and some natural emeralds do not appear red at all. The Chelsea Colour filter, originally designed for testing emeralds, will give a good indication that you may, or may not, have an emerald but will not give a simple YES or NO reading, it is more useful for the testing of other gemstones.