Question

The main constituents of pearl are:
a.) Ammonium sulphate and sodium carbonate
b.) Aragonite and conchiolin
c.) Calcium carbonate and magnesium carbonate
d.) Calcium oxide and ammonium chloride

Answer 1

Hint: Pearls consist of carbonates only. They are lustrous in nature and are used in production of jewellery.

Complete step by step answer:
Let us first discuss pearls.
A Pearl is a hard object produced within the soft tissue of a living shelled mollusc or another animal, such as fossil Conulariids. Just like the shelled mollusc, a pearl is composed of calcium carbonate in minute crystalline form, which has deposited in concentric layers. All shelled molluscs can produce some kind of "Pearl", but the great majority of these "pearls" are not valued as gemstones. Nacreous pearls, the best-known and most commercially significant, are primarily produced by two groups of molluscan bivalves or clams.

Some physical properties are:
The pearls are lustrous in nature. The unique lustre of pearls depends upon the reflection, refraction and diffraction of light from the translucent layers.
Pearls are made primarily of calcium carbonate, so they can be dissolved in vinegar. Calcium carbonate is susceptible to even a weak acid solution because the crystals react with the acetic acid in the vinegar to form calcium acetate and carbon dioxide.
The pearls are mainly used in production of jewellery. The value of pearls in the jewellery is determined by a combination of the lustre, colour, size, lack of surface flaw and symmetry that are appropriate for the type of pearl under consideration. Among these attributes, lustre is the most important differentiator of pearl quality according to jewellers.

Hence, the right answer is option (C).

Note: Remember that pearls are made up of carbonates and contain only carbonates. The carbonates used are calcium carbonate and magnesium carbonate.