floccule(n = noun.substance) floc - a small loosely aggregated mass of flocculent material suspended in or precipitated from a liquid;
is a kind of material, stuff

1.  A detached mass of loosely fibrous structure like a shredded tuft of wool. [Webster 1913 Suppl.]

2.  Specif.: A small particle of an insoluble substance formed in a liquid by the union of smaller particles. [Webster 1913 Suppl.]

floccule, n. a small portion of matter resembling a tuft of wool.