Common to all abrasives:

• we have the actual abrasive grains which are harder than what we want to grind

• the grains are embedded in a carrier material that holds the grains in place.

There is a surprisingly large number of variants:

• either the grains are so durable that they do not wear out,

• or the grains wear out, and new ones are exposed underneath and the old ones are removed,

• or the grains wear out and the whole agent is thrown away

• or the grains wear out, but break so tricky that the fractures are sharp again.