Clay Mineral Classification and Properties

These flashcards cover key terminology and definitions related to clay mineral classification, properties, and interactions.

1:1 Clay Minerals

Clay minerals characterized by one sheet of silica tetrahedron and one sheet of octahedron.

Kaolinite

A common 1:1 clay mineral with the formula Al2Si2O5(OH)4 and a basal spacing of 7.2 Å.

Basal Spacing

The distance between the layers in clay minerals; for kaolinite, it is 7.2 Å.

Van der Waals Forces

Weak forces that bond layers in some clay minerals like Kaolinite.

Hydrated Halloysite

A type of 1:1 clay with water interlayer and a basal spacing of 10.1 Å.

Non-expansive 2:1 Clays

Clay minerals that do not swell with water, such as Illite.

Illite

A non-expansive 2:1 clay mineral similar to mica, with a fixed basal spacing of 10 Å.

Montmorillonite

An expansive 2:1 clay mineral that can swell with water.

Specific Surface Area (Ss)

A measurement of surface area per unit mass of clay, with implications for reactivity and bonding.

Cation Exchange Capacity (CEC)

The ability of clay to exchange cations, expressed as milliequivalents per 100 grams of dry clay.

Isomorphous Substitution

The replacement of one cation by another of similar size in the crystal lattice of clay minerals, leading to charge deficiencies.

Charge Deficiencies

Unbalanced charges in clay particles caused by isomorphous substitution and imperfections in the crystal lattice.

Adsorbed Water Layer

Water molecules that are adhered to the surface or interlayer of clay particles, with different properties than bulk water.

Expansive Clays

Clays like montmorillonite that swell significantly upon wetting.

Hydration Energy

The energy resulting from the full hydration of cations in the interlayer of clay minerals.