212.55 carat Large Rainbow Lattice Sunstone - Australia

This orthoclase feldspar is from a very remote part of Australia - displaying both a unique pattern of aventurescence as well as adularescence.
The effect comes from lo-graphically oriented X solution crystal inclusions of Limonite & Hematite, which are responsible for the colourful aventurescence.

Aventurescence, according to Wikipedia: The effect amounts to a metallic glitter, arising from minute, preferentially oriented mineral platelets within the material. These platelets are so numerous that they also influence the material’s body colour. In aventurine quartz chrome-bearing fuchsite produces a green stone, and various iron oxides produces a red stone.

Adularescence, on the other hand, means: The effect of adularescence, also commonly referred to as schiller or shiller, is best described as a milky, bluish luster or glow originating from below the surface of the gemstone. The schiller, appearing to move as the stone is turned (or as the light source is moved), gives the impression of lunar light floating on water (accounting for moonstone’s name). Though white schiller is the most common, in rarer specimens, orange or blue lusters are produced.