The laws of grinding, mashing, and cutting small
The following section will deal with the laws of grinding on Shabbos. Grinding was one of the principal actions done in the Mishkan, as in the Mishkan they would grind the herbs to use to make dye.
The following actions are a subcategory of this principal prohibition: Cutting a vegetable very thin, cutting wood into very thin pieces in order to use to ignite a fire or in order to make a vessel, one who crumbles a thick piece of dirt in order to make a use with the crumbs.
Different foods have different laws regarding if and how they may be grinded.
 Ketzos Hashulchan 129 footnote 1