How Clay is Formed

Millions of years ago, during the Cretaceous period, the world experienced extensive volcanic activity due to the tectonic convergences e.g  of the North American and Pacific plates. During long periods of eruptions, immeasurable amounts of ash were disgorged into the prevailing easterly winds as the Pacific plate was forced under the North American plate deep into the earth’s crust. Over millions of years, the ash was repeatedly deposited in the mineral rich Mowry Sea and inter bedded with eroded silts and sediments. Slowly, the glass component of the ash was chemically altered in these low energy marine environments and consolidated into distinct layers of clay, often associated with Zeolite beds, marl, sandstone as well as shale and mud-stone.

Clay Formation

As plate drift continued, the North American plate was lifted and folded into mountains, typified by the Big Horn Mountains. The Mowry Sea drained and ash deposition subsided as the clay / silt formations were heaved upwards. The Black Hills and the Big Horn mountains were two areas thrust up during this period. These areas were eroded and weathered over time, exposing numerous clay beds that are commercially mined today.

Mineralogy – clay composed primarily of the mineral CaMg Al Si2O4. It  is a three layer mineral formed of several layers of tetrahedron and octahedron sheets, electro-statically held together by isomorphic inter-layer cations. As the electrostatic attraction is low, exposure to polar fluids will cause the formation of a monomolecular lattice of water between the silicate layers. The basis behind clay  swelling is that several layers of water dipoles can form into weak “stacked” tetrahedral structures, causing the silicate layers to separate – this is termed inter-crystalline-swelling.

 

Particle Charge – Each crystal of clay  has a large net negative charge. Thus it tends to attract any positive ions (cations), such as Calcium or Sodium ions, to its surface. The net negative charge is located inside the crystal itself. Therefore, cations tend to be attracted to the surface of the particle in an effort to neutralize the charge. The edge of the crystal has a few positive charges thus attracting negatively charged ions or molecules.

The absorbent qualities of clay make it highly beneficial in the treatment of inflammation caused by injury or illness. A clay caste (poultice) can be made by mixing clay with warm oil (e.g., olive oil) and warm water in equal parts to make an elastic paste that can adhere to the inflamed body part. Organic producers may use clay therapy to address inflammation in cattle due to foot rot, while many organic dairy producers use clay therapy to treat mastitis. The clay dressing is spread over the infected parts of the udder after milking and is allowed to dry and set for 3-4 hours. The clay mask can then be removed and repeated 2 or 3 times a day and may be left on all night after the evening milking.

 

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