The K-bearing mineral dominated in soils is

Correct option is C

The correct answer is (C) Micas

Explanation:
• Potassium ($K$) in the soil originates from the weathering of primary minerals. The most dominant K-bearing minerals in the soil are Micas (such as Muscovite and Biotite) and Feldspars (such as Orthoclase).
• Micas are phyllosilicates (sheet silicates) that contain potassium in the interlayer spaces. As these minerals weather, the potassium is released into the soil solution, making it available to plants.
• Illite is a secondary clay mineral that is also a major source of potassium in many temperate and semi-arid soils.
• Potassium is essential for osmotic regulation, enzyme activation, and stomatal movement in plants.

Information Booster:
• Feldspars constitute about 60% of the Earth's crust, but Micas are often more significant in terms of releasing available K through weathering.
• Fixed Potassium: Some K ions get trapped between the layers of 2:1 clay minerals (like illite) and are only released slowly.
• Unlike Nitrogen and Phosphorus, Potassium is not a constituent of organic molecules like proteins or DNA.

Additional Knowledge:
• Olivine (Option A): A magnesium-iron silicate; it contains little to no potassium.
• Hornblende (Option B): An amphibole mineral that contains calcium, magnesium, and iron, but is not a primary source of K.
• Zircon (Option D): A highly resistant mineral (zirconium silicate) used mainly for dating rocks; it does not contribute to soil fertility.