A rock composed essentially of a crystalline clay-like mineral formed by devitrification and the accompanying chemical alteration of a glassy igneous material, usually a tuff or volcanic ash.
Smectite refers to a family of non-metallic clays primary composed of hydrated sodium calcium aluminum silicate. Common names for smectite include montmorillonite or sodium montmorillonite ("sodium bentonite" or "Wyoming bentonite") and swelling bentonite ("Western bentonite").
Three types of bentonite:
1) Natural Calcium Bentonite or Calcium Montmorillonite
2) Natural Sodium Bentonite or Sodium Montmorillonite
3) Sodium Activated Bentonites or Sodium Activated Montmorillonites
Bentonite minerals occur as lenses or seams containing up to 50% moisture. They are rocklike in nature and usually extracted by opencast mining (quarrying).
Natural sodium bentonite as the name suggests occurs with sodium as the predominant exchange cation. The name originates from its discovery near Fort Benton, USA. Sodium bentonites are characterized by high swelling, high liquid limit and high thermal durability.
The vast majority of the montmorillonites occurring in abundance world wide are of the calcium type and referred to as calcium bentonites. The name montmorillonite originates from a discovery made at Montmorillon in France. Calcium bentonites are often characterized by much lower swelling and liquid limit values To natural sodium bentonite.
Sodium activated bentonites are produced by the substitution of calcium ions by sodium ions. This transformation can be achieved by the addition of a soluble sodium salt to calcium bentonite.
Chemical Formula: Al2O34SiO2H2O
Chemical Name: Naturally occurring hydrated aluminum silicate