So yep, exploring random mystcraft ages in my 1.6.2 instance, and come across an age with some rather large lakes of molten gold.
For anyone wondering, those tendrils are made of the TiC slimy leaves - I use the mystcraft sidekick addon which automagically adds various mod blocks as pages
And now I just found the page for molten copper in the next age I visited; guess I won't be short on that soon enough too