Sorry for the delay in getting back!
The vase has a rough texture on the outside ~ looks like it's been rolled in grit when still soft ~ but is smooth inside. The coloured pattern (reds/blues) appears to have been painted on but the deep purple colour (not grey/black!) is in the glass (I think!!). Have to say that I thought it was ceramic when I first saw it too Emmi! Glass is a reasonable thickness and appears fairly dense, especially when it's not backlit!
Thanks for the link Sue ~ had a look and it has a lot of similarities to some of the pieces there. Will keep looking!