Chelsea Colour Filter

The Chelsea colour filter (CCF) is a tool used in gemmology. It transmits only deep red and yellow-green light. The result is, some similarly coloured gems can look very different through the filter. For example syntehtic blue spinel coloured by cobalt looks pink to bright red, whereas natural blue sapphire will usually look dull or dark. This assists users to quickly spot rogue stones in parcels or multi stone set jewellery, and also as another piece of data for full gem testing. It can help differentiate many natural, synthetic, artificial or treated gemstones with experience and training. If you want to learn how to use a CCF, why not do one of our courses 😉?!