Cowboy, get one of those cheep turkey pans from the grocery store. and a small bag of fine sand from walmart.
Put the sand in the pan and bury the rock in the sand. put the pan in your oven, set oven at 250* then ramp it up 350* after 1hr than ramp it to 450* after 2hr than 500* about 45min later.. let it soak at 500* for 5-8hrs than just tern the oven off let it cool for about 4hrs than crack the door to the the oven, then let it cool for another 3hrs.
Well Paul this is how i do it. Its to easy. i would be afraid that ground cooking it might get it to hot.