I'm going camping this weekend on a site that requires me to build my fire up off the ground so the grounds of this place won't be damaged. I'm wondering if there is certain rock/stone that can be used for this or will they crack and/or explode? I know to avoid flaky rocks like shale and any rocks that seem like they may have moisture in them, but don't know much more than that. If not, do they make fire bricks that are affordable and can be used for this kind of situation? Any help would be appreciated. Thanks.