Since nobody from Arcanum has piped up yet, I can help a little.

It IS a gas burner, which means there is some sort of gas burner under the lava rock. It appears to be completely clad in natural stone, so it isn't going anywhere.

There are some tricks to doing something like this so it will work reliably and not kill anyone. There are some "off-the-shelf" components to make it easier and less expensive, but this is not a do-it-yourself project, particularly if you are using propane.