Magnesite deposits in Tamil Nadu are significant for the:

The correct answer is: a) Refractory industry.

Magnesite is a magnesium oxide mineral that is used in a variety of industries, including the refractory industry. Refractories are materials that are used to line furnaces and other high-temperature equipment. They must be able to withstand extreme temperatures and chemical attack. Magnesite is an excellent refractory material because it is strong, durable, and chemically inert.

The other options are incorrect because magnesite is not used in those industries.

• The fertilizer industry uses phosphate rock, potash, and nitrogenous compounds.
• The construction industry uses concrete, steel, and wood.
• The electronics industry uses semiconductors, integrated circuits, and printed circuit boards.