[mapt]

"grit" is usually spherical or close to it, because it has seen chemical and mechanical weathering. It is often calcium crystals of some type.

This is neither. These are long dagger shapes, significantly larger than a diatom, very hard, sharpened to a fine edge.

[tedk-42]

They aren't giving you 'microcuts' in your gut, any more than anything else.

Why? The force applied isn't in a uniform downward direction like you would with a knife.