I use that term in the broad sense, to include bitumen. Such terms refer to a range of viscous hydrocarbons, both natural and man-made. Their properties, such as colour and vicsosity vary considerably: some flow readily at room temperature, others are brittle at room temperature (such as pitch, which is interesting because its brittleness depends on how quickly it is deformed (strain rate)).
I suspect your specimen may burn if you try to light it. That would apply to both tar, wax (there are quite a few waxes, not just candle wax), and ambergris (which also smells, but is usually more of a grey colour, but can be brown). Useful intro to ambergris - http://www.ambergris.fr/identification_of_ambergris.html
So here I am expressing an opinion and thinking out loud; hope it may be of some help.
I will have a go at lighting it tomorrow and see what happens.
I had hoped that it was ambergris when I was on the beach, and that I would be in the money! But, gave up on that pretty quickly after starting internet research as no kidney-shaped structures and colour didn't look correct (plus it's rather small for £40,000!).
Thanks once again, I'll let you know how the burn goes (if you're interested?)