Clay Science

Clay Science

Type of Clay

In a clay mineral, the elements (oxygen, silicon, potassium, etc…) are spheres arranged in a regular three-dimensional pattern. The spheres are the building blocks of the clay minerals, and the arrangement of the spheres determines the type of mineral. The character of the clay mineral group determines the type of clay and its eventual use. In other words, the clay mineral structure gives us an understanding of its specific properties.

Among the clays suitable for eating, montmorillonite is the most common and the most sought after. It has been the subject of many research studies and has long been recognized by scientists and laypersons for its unusual properties. Montmorillonite clay was named after town of Montmorillon, France, where it was first identified. The mineral clay belongs to a group of clays known as smectite, a word that describes its layered structure. The smectites are one of seven clay mineral groups. Each group contains a certain number of species, variations on the layered structure. Clay minerals come in many different shapes and sizes to produce a wide variety of clays.

Because there are so many types of clay, not all of them share the same function. Some are more suited for industrials use whereas others are suited for dietary use. Of course, we are mainly interested in the clay minerals; we must study two important properties that will help us define the minerals. As we do this, we will see why more value has been placed on certain clay minerals than on others.

Absorption

Absorption is a much more slow and involved process than absorption. Here, the clay acts more like a sponge, drawing substances into its internal structure. In order for absorption to occur, the substances must undergo a chemical change to penetrate the medium’s barrier. Once it has done that, it enters between the unit layers of the structure. Instead of the toxins, for instance, sticking clays are labeled expandable clays. The more it expands and its layers swell.

Any clay mineral with an inner layer charge is an absorbent. Having an inner layer charge means having charged ions, sitting between layers, which are surrounded by water molecules. In this way, the clay will expand as the substance to be absorbed fills the spaces between the stacked silicate layers.

What makes Montmorillonite so special?

The montmorillonite minerals occur in very small particles. They are extremely fine-grained and thin-layered, more than any of the other clay minerals. The layers contain ions that are very loosely bound to one another and easily exchangeable. Not only will the toxins stick to its outside surface, but numerous elements and organic matter will enter the space between the layers.

In addition to its already unique structure, montmorillonite has a particularly large surface area when properly hydrated in water, which further boosts its absorptive and adsorptive properties. Chemically and structurally, it is shaped like a credit Card, with negative charges on the flat surface and positive charges on the edges. Therefore, the negative charge (the good one) is many times more powerful that the positive charge. Montmorillonite is a more complicated clay and has a higher exchange capacity than the simpler species of clay, such as kaolinite. Its ability to absorb and adsorb toxins is greater than that of the clays in the other groups.

According to one article on clay (Lei 1996), a mineralogist at Massachusetts Institute of Technology, Robert T. Martin, stated that one gram of this clay has a surface area of 800 square meters. To hive that some serious perspective, that’s about ten football fields! The greater the surface area of the clay, the greater the power to pick up positively charged particles or toxins many times its own weight.

Any given clay is usually a mixture of clay minerals, one or two minerals almost always being predominant. Clays are rarely found separately and are usually mixed not only with other clays but with microscopic crystals of quartz, mica, feldspar, and carbonates. Most clay contains montmorillonite to a greater or lesser degree. The available types of montmorillonite vary in color, consistency, and shape. The color may be white, gray or pink, with tints of yellow or green. Typically, montmorillonite will be included in a mixture of clay groups in any given materials; all six groups will most likely contain particles of montmorillonite. Sources of montmorillonite include the USA, Italy and France.