A crafting table is useful and all, but to properly manipulate certain materials a more specialized tool is required. A Grindstone with a marble grinding wheel does exactly that. It allows for fine adjustments to the cut and polish of different types of crystals, as well as giving the ability to grind certain types of materials into dust. A material or object can be placed onto it and then ground by right-clicking. Right-clicking with Shift [sic] will remove the item if you have an empty hand to take the item.
Handling Rock Crystals properly when trying to properly shape them and polish them is a bit of a tedious process. Frequent inspection when doing so is recommended, as inattentive grinding can reduce a crystal to nothing. Mechanical hands are incapable of operating this device due to the precision needed in crystal shaping. Perhaps things besides crystals can be sharpened in the Grindstone, as well.