“Cilantro appears to be grown in sand...”
Parsley has a lot of grit as well. Here is a trick that works: Fill the sink with water and table salt. Remove the band and swirl in the water. I even let it soak for a minute or two. For some weird reason, salted water removes sand/grit much better than regular water. Oh.. rinse the cilantro bunch (or parsley bunch) with plain water to remove any added salt flavor.
Cornmeal also works well, without the possibility of saltiness.