Abstract
Interference colour of crystals were represented in the three dimensional Munsell system and the approximate ranges for various types of abnormal colour possibly produced by crystals were estimated. The range of colour appearance considerably depends upon the type of the abnormal colour series. It is noted that, when luminosity is low, the range for the centro- and non-cyclic types are confined in an area narrower than that for the chroma-cyclic type and the colour with a low value of chroma rarely appears in the former types.
