Sepiolite is a naturally occurring, fibrous clay mineral (a hydrous magnesium silicate) that is rarely found in commercial quantities.
Whilst sepiolite has many a number of commercial applications these applications fall into two main categories – lower value applications that rely on the sorptive properties of sepiolite (e./g pet litters, animal feeds) and higher value applications that rely on sepiolite’s ‘gelling’ properties, i.e. its ability to increase the viscosity of fluids in both fresh and salt water (e.g. in oil and gas well drilling fluids, paints and coatings, and building products).
Visible at a microscopic scale, sepiolite clay is comprised of elongated fibres or ribbons which when dispersed in fluids increase viscosity. Viscosity is measured in Centipoise (cP),a unit of measurement for dynamic viscosity, which describes a fluid's resistance to flow. Liquids with higher centipoise values are thicker and flow more slowly, while those with lower values are thinner and flow more easily. For reference, water at 20 degrees centigrade has a viscosity of approximately 1cP, Molasses 5-10,000cP.
In commercial deposits the mineral sepiolite occurs in association with other clay minerals, such as saponite, and gangue minerals, such as quartz and dolomite but in commercial practice it is expensive to separate the sepiolite so the clay is characterised as either waste, medium, or high grade depending on the relative proportion of sepiolite, the quality of the contained sepiolite, and the use to which the sepiolite is intended. Generally, Spanish sepiolite is higher grade and higher quality compared to that currently mined and used in the USA. The performance of a sepiolite clay can be improved by applying appropriate minerals processing (non-separation) techniques that modify the physical properties of the sepiolite.
