Spicules are the structural components of a sponge, or the "bricks," and the shapes, sizes, and composition are unique for each species. Together, you can look at these features under a microscope to make a positive identification. Spicules are composed of either Calcium or Silica.

What is a Spicule in anatomy?

1 : a slender pointed usually hard body especially : one of the minute calcareous or siliceous bodies that support the tissue of various invertebrates (such as sponges)

What are 3 types of sponge?

Sponges were traditionally distributed in three classes: calcareous sponges (Calcarea), glass sponges (Hexactinellida) and demosponges (Demospongiae).