Is it safe to use just lodgestone to build a fire pit?

if they are fired artificial stone (such as house bricks) or natural they will be ok,

you can use any type of volcanic natural rock or stones.

but not limestone.

if they are set stones such as in concrete blocks,

then yes they could shatter or crack

and send out injury inflicting debri.

i would suggest you fire them up a few times with nobody around.

.

Sounds cool, either mold one yourself using handmade wooden cast (like boxes) or cut out a giant slab and slice a few slots in for the grill and what not.

Also remember that you can make a fire pit out of a grill and three cinder blocks if you want. I did that in my back yard when I was little and made hotdogs. Parents got pissed though. :P