Gemstone testing with the ruby filter

The ruby filter, with its specially colored glass, makes some stones appear in a different color and helps in the assessment of e.g. red gemstone lots. When viewing red or pink stones under the ruby filter, only those stones that are colored red by chrome will glow red.

• Rubies therefore appear clearly red. Synthetic rubies, red spinels and chromium-rich pyrope garnets also have a clear red coloration.
• Other red stones, however, such as almandine garnet, red tourmaline or ruby imitations show no reaction under the ruby filter. The ruby filter can also be used to identify composite stones (doublets or triplets) and glass imitations.
• Synthetic emeralds from the flux process appear in a striking, very intense red color under the ruby filter. It already conveys the suspicion of a synthesis and thus calls for further special investigations.

Color filters are no substitute for a complete laboratory analysis – but they do provide immediate, precise color information that creates a decisive advantage in the trade and in professional appraisals, for example when purchasing gemstone lots.

For a reliable investigation, we recommend a cold light source from the KRÜSS store. It allows the light to be positioned exactly where it is needed – flexibly, precisely and without any disturbing shadows.

Cold light sources are indispensable in the gemmological field, as they illuminate even complex-shaped objects evenly and without shadows using a double light guide. Our models impress with their mechanically adjustable intensity without color change and a long-life halogen reflector that ensures consistently high light quality.