Clay minerals are a group of hydrous aluminium phyllosilicates, characterised by two-dimensional sheet structures. Variable cation substitution in these sheets leads to differential layer charge which result in changeable reactions with water and organics together with high surface area and cation exchange capacities.
Clay minerals can be divided into four major groups: kaolin, smectite, illite and chlorite. Each of these groups exhibit different characteristics. Clay minerals are typically fine-grained (4 μm) and constitute about 16% volume of material at the Earth's surface and are abundant in soils, sedimentary and low-grade metamorphic rocks and hydrothermal alteration zones.
The importance of clay minerals
Studies of clay minerals are imperative for a wide range of stakeholders, for example:
soils and agronomy – clay minerals are fundamental to many soil functions including water, nutrient (e.g. potassium, ammonium) and contaminant (pesticides, heavy metals) retention, carbon storage, maintaining soil structure and the filtering of both ground and surface waters
civil engineering including waste disposal – due to their large shrink-swell and sorptive capacities, studies of clay minerals are essential to site assessments and geotechnical investigations. Clay minerals are also frequently employed as engineered materials.
energy – studies of clay minerals may be employed to detect the depositional environment, stratigraphic correlation, reservoir quality, cap rock properties and basin history of hydrocarbon deposits and for carbon capture and storage
industry – clay minerals form critical raw materials for a range of industrial processes including catalysis, colloids, paper coating, drilling fluids, pharmaceuticals, ceramics and nanocomposites
Characterising and studying clay minerals
BGS has provided a centre of excellence for the study of clay minerals since the 1960s and continues to research these important minerals using a range of analytical methods available at the Keyworth laboratories:
The study of clay minerals plays a key role in projects that span the BGS science programme. Current examples include:
the characterisation of host rocks and engineered backfill materials for radioactive waste repositories
studying the impact of land management practices on the sustainability of soils
the characterisation of reservoir and cap rocks for hydrocarbon exploration and carbon capture and storage projects
researching the low grade metamorphism of Lower Palaeozoic strata in southern Scotland and central Wales using illite crystallinity
the characterisation of UK rocks and soils to understand and predict their engineering properties
Staff and facilities are also in constant demand for direct consultancy analysis and interpretation by external clients including: oil, mineral and mining companies; engineering and utility companies; consultancies; university departments and local authorities.