This is a faceted disk that is curved in opposite directions, so it gives the illusion of twisting. The facets also run in opposite directions, so that the straight slat facets appear as a checkerboard instead. This is designed as a sew-on stone for decorating fabric - hence the two holes - but talk about fabulous for bracelets or necklaces - connect with chain or jumprings? Definitely don't see this colour in this shape very often.
18mm x 18mm x 6mm Hole size is approx. 3mm. By the each.