I have a stone which I bought from an antiques shop many years ago.
I was told it was used by man, stone age etc, for being heated up by fire then used like a heater.
The stone itself is really smooth and a stained like a brown colour, it's like a large egg about 6 inches in length, quite heavy..
Photos available if anyone wants one.
I don't really know much about ice age heater stones, but I would imagine it would have more cracks. It looks like jasper.
I may be wrong, but if it was ever put in a fire, even thought it has got a few cracks, I think it would have more cracks.
Your specimen looks to me to be from a beach system were it has spent some time, similar to a stone tumbler that smooths off the pebbles.
The stained brown colour could be from minerals in the ground or pyrites as Mike suggested, or from repeted heating up in a fire.
Did stone age man use these 'hot rocks' for other things other than pot boilers?
I think you may have been had by that dealer. If it had been heated, the rock would become more brittle and with repeated heating and cooling begin to appear more glass like and cracked. This looks like a concretion which has been rolled around on a beach or river and then been polished, presumably by hand giving that the stone is polished even on the inside of the small craters and imperfections of the rock. Sorry if this is a little disappointing but it is still an attractive object in my opinion - reminds me a little of the style of salt glazed stoneware.
I agree with the UK fossil guy- the dealer wasn't actually sure what it was. It is quite common when a dealer finds or buys something, and they just make it up what it is when they don't know, but by no means are all dealers like that.
Most dealers are genuine people, it is is just the odd few which con people. I buy loads of fossils. When you type in fossils for sale on google, the first 20 which come up are surtain to be genuine, and even the ones after that are probably genuine- it is just the odd few which con people.
Yeh, at least it was only Â£7. I once bought a spinosaurus tooth when I was about 3. At the shop, they said it was the complete tooth which didn't have any repairs, but now I am older I can tell it has 8 repairs, and the only real fossil part to it is a tiny piece of enamel. The rest of it is just man-made rock.