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Palmer Coking Coal Company markets several types of clay and silty sand products.  Our primary clay product is a basic Gray Clay composed of fine sands, silt, and clay.   In characterizing soil, the “size consist” of the soil particles determines how the soil is classified.  Sands are the larger particles and for that reason are generally better drained.  Next comes silt, while the finest or smallest particles are the clay fraction.  The greater the amount of clay, the less permeable the soil and the harder it packs.  With clay, like most products, there is a tradeoff between purity and ease of handling.  Without some sand and silts, pure clay when wet would be very “sticky” and difficult to work.  The inclusion of some sand and silt makes the clay soil more workable and improves its flow characteristics.  A good way to think of flow characteristics is to contrast the way sugar or salt flows as compared to the way very fine flour or corn starch might flow.

 Clay is useful in a number of applications where the user needs a hard packed material with low permeability.  Water percolates through clay soils very slowly when compared to a rapid permeability material such as drain gravel.  Applications for our clay products include compaction grouting, horse stalls, BMX bike trails, a barrier soil liner for ponds, ditches, landfills, streams, or as a soil or soil amendment where a denser clay consistency is required. 

 Typical sieve or particle size analyses for our Gray Clay is shown below (product sieve sizes can change so please call for our most recent analysis):

Sieve % Passing
5/8” 99%
#4 84%
#8 76%
#16 66%
#30 49%
#50 31%
#100 23%
#200 19%


Unique Characteristics of Clay
by Alfred R. Conklin, Jr.


Soil is made up of three different size solids - sand, silt, and clay.  Of these, the smallest are the clay particles. Though many soils contain gravel, rock, and boulders, all contain sand, silt, and clay.  Here however, we are only thinking of the clay fraction.  Soils are said to be “clayey” over a broad range of clay contents.  Any soil with a clay content of 30% or more will have clay as part of its textural name.  Clays, along with organic matter, are highly active both chemically and physically.  It is this high reactivity that makes clay an important consideration in all the uses to which we wish to put soil.

Clays are not smaller versions of sand or silt particles which are primarily silica.  They are formed chemically by substitution or rearrangement of primary minerals, or by crystallization of aluminum and silicon oxides from the soil solution.  Soil contains many different types of clays.  The important differences are not in size but in chemical make up, crystal arrangement, and isomorphous substitution.  Clayey soils have high water holding capacity and low to extremely low hydraulic conductivities.  They also have high chemical reactivity.






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