Biominerals (pearls): What are the principal constituents of natural pearls? Identify the mineral phase and the organic matrix secreted by molluscs. Choose the correct pair.

Given data

• Object: Natural pearls (nacre).

Concept/Approach
Pearls consist mainly of aragonite (a crystalline form of CaCO₃) arranged in platelets, bound by an organic protein–polysaccharide matrix called conchiolin.

Reasoning
Aragonite (mineral) + conchiolin (organic) → nacre's layered structure and luster.

Common pitfalls
Confusing aragonite with calcite (another CaCO₃ polymorph) or pairing with unrelated salts.

Final Answer
Aragonite and conchiolin