The colours on my monitor are all weird and washed out, but the vase in the link you give Spacey, does not look nearly as elegant as yours, and it's NOT what I would call "Chalcedony" either - neither is yours.
Do you know of any English (or American for that matter) companies who used mica flake inclusions, Christine?
The only maker I know of at all, other than Monart, who used them, is the unknown Bohemian one.
I would describe the decor on this flask as spattered over a white background, with mica flake inclusions.