Assertion: insect's exoskeleton | /r/MadeOf | various materials – silica
Facets:
Source sentences:
text: It is known, however, that in a very short course of time, just before the Cambrian period, exoskeletons made of various materials – silica, calcium phosphate, calcite, aragonite, and even glued-together mineral flakes – sprang up in a range of different environments.