It comes in a few forms in the UK "pure" and "blended." The pure is oil is what it says it is. The blended oil can contain petroleum products and/or be refined from lard. The pure variety is animal based, the best type coming from the shins of calves. It is still refined in the US despite what Kingsmere Crafts says - Welch even produce a kosher variety - so there can hardly be any pig-parts in that particular pot!

Regards,
Neil