Smektiittimineraalit

Smektiittimineraalit are a group of phyllosilicate clay minerals belonging to the smectite family. They feature a characteristic octahedral–tetrahedral–octahedral layer arrangement, often described as (O–T–O). The octahedral sheets are usually composed of magnesium, aluminum, or iron, while the tetrahedral sheets are dominated by silicon and aluminum. Whole layers are bonded by expansive interlayer cations such as sodium, calcium, or magnesium, which also balance the negative layer charge.

The most well‑known smectite minerals are montmorillonite, beidellite, and nontronite. Montmorillonite is the most abundant worldwide and has a high capacity for swelling and water absorption owing to its extended interlayer space. Beidellite contains a significant amount of aluminum substituted for silicon, whereas nontronite is iron‑rich and often forms in alkaline, oxidizing environments.

Smektiittimineraalit form in a variety of geological settings, including sedimentary basins, volcanic ash layers, and hydrothermal veins. They develop through the alteration of volcanic ash, feldspar‑rich sediments, or bauxite. Their expansive properties make them useful as drilling muds, sealants, and carriers of agricultural nutrients. In environmental engineering, they serve as adsorbents for heavy metals and radionuclides, and in the oil and gas industry, they help stabilize cutting fluids.

Physical properties of smectite clays include low bulk density, high specific surface area, and a tendency to dehydrate and resume water adsorption with temperature changes. These attributes influence their mechanical behavior, making them prone to plasticity and consolidation when saturated. Their reactive nature, combined with their widespread occurrence, has made smektiittimineraalit a subject of ongoing research in mineralogy, material science, and environmental studies.