A set of 6x acrylic colour filters in Red, Yellow, Green, Light Blue, Dark Blue and a frosted “White” (diffuser). Insert a colour filter between the light source and the stone to enhance both visibility of features in stones and the observation of spectra. As an example, curved colour banding difficult to see in yellow Verneuil synthetic sapphire becomes more apparent when using the blue colour filter over the light source (the complementary colour to yellow). Coloured filters enhance features in coloured stones, whilst the frosted white filter may enhance features in colourless stones. In spectra, the colour filters can enhance lines that may otherwise be missed – examples can be found on pages 36 & 37 of A Student’s Guide to Spectroscopy by Colin Winter, 2nd edition, OPL Press.