The main constituents of pearl are

The principal constituents of pearls are the mineral aragonite (a polymorph of calcium carbonate) and an organic protein called conchiolin. Nacre—mother-of-pearl from which pearls form—is a composite of closely packed aragonite tablets (~95% CaCO3) bound by an organic matrix; this mineral-organic structure is repeatedly cited [2]. Reviews and materials analyses of pearls and pearl powder state pearls contain predominantly calcium carbonate in the aragonite form plus organic proteins and other minor components, matching the term “conchiolin” for the organic binder [3]. Therefore among the options, “aragonite and conchiolin” correctly names the mineral and organic constituents that make up pearls. This matches option 2.

Sources

1. [1] https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/nacre
2. [2] https://ris.cdu.edu.au/ws/files/43902951/materials_14_02797_v2.pdf
3. [3] https://pmc.ncbi.nlm.nih.gov/articles/PMC9445187/