Size: 14.6mm by 20mm 

Colour: white with rainbow overtone

Shape:  hard to describe..look at the photo. it's got pointy bits

Surface: fairly smooth. Hole in the back

Lustre:  satin/metallic

Drilled? undrilled

selected by Pearlescence. Defies categorisation. Definitely a one-off. Flat to base. Would set as a fabulous pendant perhaps.