Bentonite forms from alteration of which material?

Bentonite forms from alteration of which material?

• A. Limestone
• B. Sedimentary peat
• C. Volcanic ash
• D. Glacial till

Answer: (C)

Bentonite is a swelling clay produced when volcanic ash is altered in the presence of water. Weathering of the glassy components in volcanic ash forms clay minerals in the smectite group, especially montmorillonite, which gives bentonite its characteristic expansive, plastic clay properties. This source is unique to volcanic ash deposits, unlike the other options: limestone is calcium carbonate from shells and reefs, peat is partially decomposed plant material, and glacial till is a mixed sediment without a distinctive alteration to smectite clays.

Bentonite is a swelling clay produced when volcanic ash is altered in the presence of water. Weathering of the glassy components in volcanic ash forms clay minerals in the smectite group, especially montmorillonite, which gives bentonite its characteristic expansive, plastic clay properties. This source is unique to volcanic ash deposits, unlike the other options: limestone is calcium carbonate from shells and reefs, peat is partially decomposed plant material, and glacial till is a mixed sediment without a distinctive alteration to smectite clays.