Mystery brooch - German sterling, but what's the blue stone?

The frame is marked Sterling and Germany, obviously made for export. The stone looks like jasper or some other "random pretty rock", but it's mostly blue. Some sort of chrysocolla maybe?

 

Looks like the remains of an icky sticker on the back. Have you swiped it down a bit? It's very dark in the pictures.

 

It is dark, but the pictures are a little darker. The sticker ick has been there longer than I've had it; it feels calcified, so it's been there a good 30 years as is.

 

Yes, I'd say chrysocolla, which is also mined in Germany.
If it were Israeli it could be Eilat stone, a combination of chrysocolla with azurite, malachite, and turquoise.
I have edited your photo a bit, it is far too pale now, but you can see the beautiful definition in the stone:

 

Hi joolies
Evely, your stone is a blue stained jasper, called either Swiss or German lapis!
Here is a similar brooch:
http://www.ebay.fr/itm/Art-Crafts-S...119832?hash=item1eab030198:g:bGQAAOSw~OdVfNgp