Clay has been formed for millions of years, since the time of the glaciers. No clay deposits are exactly the same and, typically, mineral clays are mixed in various proportions. Clay deposits which remain in the place they were formed are called primary clay. Clay which moves from its original location by water erosion is known as secondary clay. Clay particles are about 20 times smaller than silt. Clay is made up of tiny platelets; when you mix clay with water and manipulate it, these platelets slide over one another and make the clay plastic.
Silts, on the other hand, are crumbly in texture. Many naturally occurring deposits include both silts and clay. Where to dig So… first you must find your clay. Larger particles are filtered out through rocks and sand, leaving silt to settle into beds of clay. How far silt travels from its source and how pure the silt is determines the type of clay it becomes. Most clay minerals form where rocks are in contact with water, air, or steam.
Examples of these situations include weathering boulders on a hillside, sediments on sea or lake bottoms, deeply buried sediments containing pore water, and rocks in contact with water heated by magma molten rock. All of these environments may cause the formation of clay minerals from pre-existing minerals. There are 2 clay types -. Bentonite is also used as a soil liner for environmental containment applications and with polyacrylamide for making paper.
Weathering of rocks and soil is the primary way that clays and clay minerals form at the Earth's surface today. The weathering process involves physical disaggregation and chemical decomposition that change original minerals to clay minerals; weathering is uneven, and many stages of breakdown may be found in the same clay sample.
Factors governing rock weathering and soil formation include the initial type of rock, the ratio of water to rock, the temperature, the presence of organisms and organic material, and the amount of time. The types of clay minerals found in weathering rocks strongly control how the weathered rock behaves under various climatic conditions such as humid-tropical, dry-tropical, and temperate conditions. Kaolinite is found in most weathering zones and soil profiles.
Montmorillonites, which are chemically more complex than kaolinites, are common in the lower parts of weathering profiles, nearer the rock, where chemistry exerts a strong control on mineralogy. Complex mixed-layer clay minerals such as illite-smectites are abundant in clay assemblages that develop from mica-bearing precursor rocks, such as the granite plutons that occur in temperate regions of the Northeastern United States.
For example, a large component of soils formed by weathering of granites may consist of metastable muscovite, biotite, and chlorite. These minerals will alter progressively to clay minerals. Industrial minerals, such as clays, sand, gravel, and crushed stone, are raw materials used for building and maintaining infrastructure, agriculture, and mitigation of environmental problems.
Because of the many uses for industrial minerals in our society, land management agencies have an increasing need for better geologic and mineralogic data on industrial minerals. The USGS supports studies to understand the geology of these deposits, the surficial environments, and the processes by which these deposits form. The USGS and industry cooperators are initiating petrologic, mineralogic, and geochemical studies to better determine how economic clay deposits form.
A special emphasis of these studies is to characterize the weathering portion of the life cycle of a clay deposit. Regional data bases such as the Southeastern United States clay deposit data base are being developed that contain geologic and geochemical information necessary to establish environmental characteristics that affect the use of clays and clay minerals.
The alluvial deposits that you find today did not happen anytime in the near past. It would have taken hundreds to millions of years for these depositions to happen such that the clay is present in appreciable quantities today.
Alluvial deposits are not always in a river or near a river. For most people, it is just easier to look for where a river currently is and test their lucks there. More often than not, they want you to work for it too. When digging through them, it is not uncommon to be faced with layers of silt, sand, gravel, and loam before you start finding clay. The kind of materials that the clay has picked up while in transit will also impact the quality.
On average, though, you will find good clay here. Take a look at the bright colors of the Grand Canyon. Get familiar with that color before you embark on your quest for clay in a marine deposit. Like the above, they are also deposited by water bodies. Unlike the above, they are a result of the work of seas and lakes.
They will, thus, be of a higher quantity than those deposited by rivers. Another similarity between alluvial and lacustrine deposits is how there are different layers of different materials. That said, you should also not only look for where seas and lakes currently exist. I know that searching near where these water bodies used to exist or pass through does not sound easy. However, find one and you will have an endless supply of good clay for a long time to come. The mistake that most people make is thinking that they cannot find glacial clay deposits in their area.
That would sound logical if you are not in a polar climate kind of location. If the science of climate change is anything to go by, though, you know that an ice age from years ago could have had glaciers in your area.
Sometimes, you find them on the topsoil itself or just buried under this soil. This is one feature that they share with primary clay deposits. Some of the basic tell-tale signs of glacial clays on normal-looking land include, but is not limited to:.
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