Question

Most easily weathered mineral is _______

• A. Olivine
• B. Ilmenite
• C. Orthoclase
• D. Quartz

Hint:

Goldich's Weathering Series mirrors Bowen's Reaction Series. Minerals that form first at high temperatures (like Olivine) are the most easily weathered, whereas minerals that form last at low temperatures (like Quartz) are the most resistant to weathering.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Mineral weathering rates on the Earth's surface depend on the crystallization temperature of the minerals during magma cooling.
Goldich's Weathering Series (1938) established that minerals that crystallize at high temperatures and pressures (early in Bowen's Reaction Series) are the least stable and most susceptible to chemical weathering under surface conditions.

Step 2: Detailed Explanation:
According to Goldich's Weathering Series, the stability of common silicate minerals is inversely proportional to their crystallization temperature.
Olivine: This mineral crystallizes first at extremely high temperatures and pressures, featuring isolated silica tetrahedra bonded by iron and magnesium.
Because its structure forms under conditions vastly different from the surface environment, it is highly unstable and is the most easily weathered mineral.
Orthoclase (Potassium Feldspar): This mineral crystallizes later at lower temperatures, featuring a more complex framework silicate structure.
It is moderately resistant to weathering.
Quartz: This mineral crystallizes last at the lowest temperatures and has a highly stable, tightly bound three-dimensional framework of pure silica.
It is the most resistant mineral to chemical weathering.
Ilmenite: This is an iron-titanium oxide mineral that is highly resistant to weathering, often accumulating in heavy mineral sands.
Therefore, Olivine is the most easily weathered mineral.

Step 3: Final Answer:
Olivine is the most easily weathered mineral among the choices, which corresponds to option (A).