I think this is Lapis Amethyst, some of my Nail Prism bottles aren't very well labelled but as far as I can tell by Googling swatches this is what it comes closest to, so for the purpose of the post let's say this IS Lapis Amethyst.
These pictures are two coats over Barry M Gelly Hi Shine in Blueberry, which is a pale blue shade, I think next time I'll try it over a darker base. From the swatches I have seen it seems to bring out the duochrome more when you use it over a dark base.
The polish is a pale shimmery blue colour with a lilac pink duochrome effect.
From some angles the polish is very blue while from others you can really see the lilac and pink shades.
This polish reminds me of Models Own Indian Ocean, of the two Indian Ocean has better sparkle and wow factor although Lapis Amethyst is a little more duochrome in the traditional sense.