Lierbachtal Thunderegg with Cloudy Purple Core

Here's a little Lierbachtal thunderegg that has got me puzzling. It was part of a cheapish bundle deal (with a handful of other rocks that went straight into my shop pile!) and the only reason I bought it. When I bought it, the term amethyst was bandied around, but now I actually see it - well, I never really saw anything like it before! The purple smudging gives way to distinct purple needles within the cloudy white crystal in the centre.

8cm