Thank you one and all for your replies. My dad has the rock so I'll ask him for more information based on everyone's responses.
@Goldfreak
I haven't put a flame to it but I'll ask my father to do so and report the outcome but I expect it to have no effect. I'm not sure whether the orange bits are soft or not, I think they are, but viewed under a magnifying glass shows all the orange bits have a spiral pattern to them.
@aussiefarmer
It has no smell to it at all.
It's very solid & quite heavy, heavier then most rocks of similar size. Also, it has no attraction to a magnet if that means anything.
I'm trying to gauge whether it is rare or worth anything and based on the responses so far, I'm guessing it might just be a rock.
Thanks all.