From Minetest

Groups is a concept for Nodes, Items and Tools in Minetest. Any of these may be a member of a group or multiple groups, or none at all. Groups are used mainly for crafting recipes, to determine damage, to determine digging time and lots of other stuff as well.

List of ordinary groups used by crafting recipes

Also mentioned are the members in the groups as seen in Minetest Game. Mods may add other items which become members of these groups, so this list is neccessarily incomplete.

List of known groups that determine damage and digging time

  • oddly_breakable_by_hand: can be broken by hand.
  • crumbly: stuff like dirt and sand. Shovels are great to break nodes in this group.
  • cracky: tough but crackable stuff like stone. Pickaxes are great to break nodes in this group.
  • choppy: something that can be cut using force; eg. trees, wooden planks. Axes are great chopping these down.
  • fleshy: living things like animals and players. Swords deal great damage to them.
  • snappy: something that can be cut using fine tools; eg. leaves, small plants, wire, sheets of metal. Swords can be used to dig these, but they wear out quickly.
  • explody: especially prone to explosions.

List of special groups (excerpt)

  • dig_immediate: block can be immediately or almost immediately be dug.
  • soil: saplings will grow on blocks in this group.

List of other groups (excerpt)