Assertion: mollusk's shell | /r/HasProperty | calcium carbonate
Facets:
value: with a small quantity of protein
type: OTHER
value: mostly
type: DEGREE
Source sentences:
text: The shell of a bivalve is composed of calcium carbonate, and consists of two, usually similar, parts called valves.
text: Such shells have three distinct layers and are composed mostly of calcium carbonate with only a small quantity of protein--no more than 2 percent.