Poetry clay, fire clay, bentonite clay, red or gray bank clay…
Any of them will do the job, you can use sand or crushed brick (or pottery) about 1/2 ratio. (I part clay,2 parts sand) makes a good adobe. The mix is fairly forgiving. 1/4 clay works, as dose 1/2 sand. Remember that natural soil will have silt so that’s why clay/sand doesn’t always make 100%.
welding is the only time I melt bricks, so most the time it’s not a problem.