Granite is normally graded in either weight or by the foot i.e 1-2ft boulder, 2-3ft boulders. This material is more rugged in shape, and most quarries blast it out of the side of mountains and then send it to you or the supplier in trucks. Shapes are irregular and harder to work with. Most of the time to build any substantial sized rock retaining wall, you’ll need machinery like a bob-cat or excavator.