Large Picture Jasper Crystal Tower 15.5cm Last Chance but it is thought that but it is thought that Undulatory Extinction occurred during the metamorphism process of the rock and this facilitated the unique composition and structure of the stone that lends it well to the Rayleigh Scattering effect of light scattering (which is thought to be behind the observable blue colour of the Quartz) Purple Moss Agate is a unique purple variety of the typically green and white coloured Moss Agate (Tree Agate) that contains translucent Purple Chalcedony which displays patterns similar to landscapes in the form of black dendritic markings or colourful veins created during the silification process of the Jasper but care should still be taken not to damage the crystal surface