Assertion: sponge's spicule | /r/AtLocation | nature
Facets:
Source sentences:
text: Spicules are calcareous (consisting of Calcium Carbonate or Calcite; these spicules occur in the class Calcarea of phylum Porifera) or siliceous (consisting of colloidal Silica or Silicon; these spicules occur in the class Hexactinellida of phylum Porifera) in nature.