you need to check local code but I think the black pipe is the only thing allowed. and it has to be a certain amout into the ground, like electric has to be 18".

There is a plastic pipe that is used for gas, it is yellow in color, and can be found at Home Depot. DO NOT use galvanized pipe for ANY gas lines whatsoever!!!! For inside work Black pipe is what you would use. Check with your local gas company and the building department regarding burial depth and materials.

You cannot burry black pipe, you must use the yellow plastic..as mentioned above..