The above methods are only useful for cabbing material of moderate value. You would never want to hammer an expensive piece of rough where the loss would amount to much money. Nor would you want to use the technique on something fragile, like opal or calcite. Expanding fractures would reduce the useable areas and value of the material too much to be worth the savings in labor. For these materials, saws and tile nippers are called for.
Lapidaries use slab and trim saws.
The difference is the size blade they use. Trim saws have small, thin blades that remove a minimum of material. Slab saw blades are thicker, because they are designed to do heavier cutting. Trim saws use 4 to 6 inch blades that run between .004 and .012 inches thick. Diamond blades are like a revolving finger nail file.