Pearl is a hard object produced within the soft tissues of a mollusk. Which one of the following is the main constituent of pearl?
[amp_mcq option1=”Calcium carbonate” option2=”Calcium oxide” option3=”Calcium nitrate” option4=”Calcium sulphate” correct=”option1″]
This question was previously asked in
UPSC CDS-2 – 2017
The main constituent of pearl is calcium carbonate.
Pearls are formed within mollusks when an irritant, such as a parasite or a piece of shell, enters the shell. The mollusk secretes layers of nacre (mother-of-pearl) around the irritant as a defense mechanism. Nacre is composed primarily of microscopic crystals of calcium carbonate (CaCO3), mainly in the aragonite form, cemented together by an organic protein matrix called conchiolin.