Here we have the three mortar and pestle pieces our house possesses.
(reading that all I hear are my professors telling me to stop using the passive voice)
You might not even have one mortar and pestle in your household, and that’s fine. We only had two until someone decided to get us one for Christmas, not knowing we had already managed to locate some for our uses. They are obviously of varying quality, and we use them for different things around the house.
The plain white ceramic piece is my “crafting” mortar and pestle. I sometimes add pigments purchased in the form of pastels, chalks, or watercolor paints to add to various projects. Grinding them into a powder is usually necessary, and few things work as well as a mortar and pestle. It is a cheaper version than the other two, but works better for my purposes since it has a small spout on the side.
Only $10 at Ax-Man Surplus it has served me well for several years and is sturdy enough, though I doubt it would survive much of a fall. It was in with the chemistry supplies though I haven’t seen any since I purchased mine. I don’t know what price it might be elsewhere.
The other two we use for various cooking things (especially crushing Oreos for truffle making at Christmas time). The white tends to be used for spices, and the green for everything else. While we certainly only need two around the house, it is nice to have a third. They tend to be much more expensive ($30-$50) but can survive drops onto soft surfaces easily and harder surfaces would probably take quite a few times over the years.
Using a mortar and pestle is pretty self-explanatory, you drop what you would like to pulverize into the mortar (bowl piece) and use the pestle (other piece) to crush it. Depending on what you’d like to smoosh, more pressure or less pressure might be used, and circular grinding strokes or jabbing thrusts.
The shape of the pestle is going to be a factor in how effectively you can crush things and also on how tired your arm/hand may become. The shape of the mortar can affect whether things “run away” from the pestle. If you’re going to be crushing smaller, round things, you probably want a smaller mortar. Crushing peppercorns in my craft mortar and pestle would be an infuriating task (if I needed to for some reason).
Overall, if you have been dealing with a plastic bag and a rolling pin, you might save yourself some headache picking up a mortar and pestle instead. They can also provide some kitchen decor, depending on what type you pick up. If you don’t have a use for one, however, I think this is one of those tools you can get by without (see bags/rolling pins as above).