A suribachi is used to grind and crush things, mainly seeds to make sauces and dressings. They work much better than a food processor for grinding fine seeds like sesame. Suribachi are sold in a wide range of size. However, a medium (7-10 inches) sized one will be the easiest to use.
It’s a clay bowl with sharp ridges on the inside surface. The exterior is glazed pottery, usually brown in color. A wooden ‘stick’ or pestle is used to do the actually grinding. To clean, gently hand wash.