What do you understand by :
Bentonite

Explanation

### Step-by-Step Solution:

1. **Definition of Bentonite**:
- Bentonite is defined as an absorbent swelling clay. It is primarily composed of a mineral called Montmorillonite.

2. **Formation of Bentonite**:
- Bentonite typically forms from the weathering of volcanic ash. This process occurs when volcanic ash is exposed to seawater, which leads to the conversion of volcanic glass present in the ash into clay minerals.

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