Stuff is like (and likely contains quite a bit of) liquid mercury.

It's actually mostly gallium, the other element that is liquid close to room temperature:

http://www.coollaboratory.com/pdf/safetydatasheet_liquid_pro_englisch.pdf

Given that spec sheet, Liquid Pro it is most certainly Galinstan, or a slight modification of it.

http://en.wikipedia.org/wiki/Galinstan

That's actually quite cool. Good find.