LearningGeo

Clay Mineral Structures
Clay minerals are comprised of silica tetrahedra and alumina octahedra, a silica tetrahedron is a silicon ion surrounded by four oxygen ions. Planes drawn through lines connecting the oxygens atoms define a tetrahedral (four-surfaced) shape. An alumina octahedron is an aluminum ion surrounded by six oxygen or hydroxyl ions. Planes drawn through lines connecting the oxygens and hydroxyl atoms define an octahedral (eight-surfaced) shape.