CLAY TYPES

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CLAY TYPES

http://www.enrgworks.com/ch/clay_types.htm

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 mineral, 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.

 

 

 

The three-dimensional pattern of the clay mineral. Whatever sits in the middle, in this case the silica element, determines the type of clay and what it will do. The name of this mineral structure is single silica tetrhedron, and it is the building block of montmorillonite clay (the best for eating). Among the clays suitable for eating, montmorillonite is the most common and most sought after. It has been the subject of many research studies and has long been recognized by scientist and laypersons for its unusual properties. Montmorillonite clay was named after the 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 industrial use whereas others are suited for dietary use.

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WHICH CLAY WILL DO WHAT?

There are seven groups of clay. They are as follows:

Kaolin group

Illite group

Smectite group

Chlorite group

Vermiculite group

Mixed-layer group (consists of all five groups above)

Lath-form group

All clays will adsorb; however, the smectite group is the only one capable of absorption. Most clays sold in the health food industry belong to the smectite category.

Kaolin

Kaolin is the mineral clay used in Kaopectate. While it absorbs toxins and bacteria like the other clays, it primarily acts as a bulking agent and serves an antidiarrheal purpose. Recently, several health food companies have advertised kaolin as a part of their mineral complexes, emphasizing its trace mineral benefits.

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Illite

The illite group is named for the state of Illinois. The best-known species of illite is glauconite, a green mineral clay. It is typically found in clays of marine origin. Other colors include white and yellow.

Smectite

Smectite is characterized by its expandable properties. Unlike the other clays, only smectite can absorb toxins. This qualifies its structural uniqueness and sets it apart from all other clays. For this reason, smectite has become a favorite clay for industrial and dietary use.

The most familiar species of smectite is montmorillonite. Again, it is the most preferred species of edible clay. Most clay research has been done with montmorillonite.

What Makes Montmorillonite So Special?

The montmorillonite minerals occur in very small micron sized 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 adsorptive and absorptive 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 adsorb and absorb 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. Marin, stated that one gram of this clay has a surface area of 800 square meters. To give 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 the 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 tan, with tints of yellow or green. Typically, montmorillonite will be included in a mixture of clay groups in any given material; all six groups will most likely contain particles of montmorillonite. Sources of montmorillonite include the United States, Italy, China and France.

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Bentonite

Sodium-bentonite is a commonly and highly utilized industrial clay. Currently, several companies are selling calcium bentonite in health formulas. Bentonite is widely distributed in nature. Its name was derived from the Fort Benton series of cretaceous rocks in Wyoming, where it was first found. The name can be misleading; sodium-bentonite is not a mineral name but a trade name for a commercially sold swelling clay. It is often used in commerce as a name for montmorillonite, and sometimes the names are used interchangeably. Smectite is the general group name used by mineralogists.

The source of bentonite is weathered volcanic ash. In marine environments, the ash transforms itself, over time, to smectite. There are several species in the smectite group, montmorillonite being one of them. Depending on its source, bentonite may contain a high percentage of montmorillonite or just a tiny bit. The rest of the contents may either be related or a completely different mineral group. Rarely does 100 percent pure smectite occur: therefore, not all bentonite is a pure smectite. Quite commonly, the clay minerals illite or chlorite are present in alternating layers.

When choosing the right clay to eat, be aware of this. Bentonite is sometimes wrongly sold under the montmorillonite label or, at least, the name doesn't give any clear indication of its contents. There are a wide variety of bentonite clays that looked, felt, tasted, and acted differently from the others. They did so because they were not the same clays. The variation in minerals does not really matter in industrial use, so long as the bentonite has good expansion capacity. But the guidelines for industry use do not hold for the consumption of clay. Unfortunately, because some clays vary in contents, some are better suited than others for eating.

This tends to be confusing, and it seems uncertain exactly which clay mineral is actually aquired even when the label says "bentonite." Even the scientists have differing opinions or are not sure themselves.

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Single-and Mixed-Clay Minerals

Typically, any given clay material may be composed of particles of a single clay mineral or a complex of many different naturally occurring minerals. It is not easy to find pure samples of many clay minerals. When they are found in nature, like a vein of gold, they are painstakingly mined. Otherwise, scientists depend on preparing single-clay minerals in the laboratory.

Most commonly in nature, layers of one type - for example, montmorillonite - are interlayered with units of another type, for example, illite. In other words, a tiny particle may be composed of successive layers of illite and montmorillonite. This of course varies according to the region of the deposit and the climate. Climatic effects influence the occurrence of certain minerals.

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