Which amidst the following is not a gem stone ? A. Cat’s-eye B. Topaz C. Opal D. Pearl

The answer is D. Pearl.

A gem is a precious or semi-precious stone that is used in jewelry. Some common gems include diamonds, rubies, sapphires, and emeralds. Pearls are not considered to be gems because they are not formed from minerals. They are formed when an irritant, such as a grain of sand, enters an oyster and the oyster secretes a substance called nacre to coat the irritant.

Over time, the nacre builds up and forms a pearl.

Cat’s-eye is a type of quartz that has a chatoyancy, or a band of

light that appears to move when the stone is moved. Topaz is a type of aluminum silicate that can be found in a variety of colors, including yellow, blue, and pink. Opal is a type of silica that is known for its play of color.