Assertion: valve | /r/MadeOf | either calcite
Facets:
value: with forming an inner layer
type: OTHER
Source sentences:
text: The valves of the shell are made of either calcite (as with, e.g. oysters) or both calcite and aragonite, usually with the aragonite forming an inner layer, as is the case with the Pteriida which have this layer in the form of nacre or mother of pearl.
text: The valves are made of either calcite, as is the case in oysters, or both calcite and aragonite.