I. Monosiallitic Assemblages
 

Kaolinite, halloysite and or fully hydroxy-Al interlayered vermiculite (HIV) dominate the clay fraction. Often present but not necessary are lesser quantities of mica and oxyhydroxides of Al and Fe. If smectite is present it should be at low concentrations such that it is not identifiable by appropriate mineralogical analyses (usually less than 10%). Usually the clay fraction CEC at pH 7 is < 30 meq/100g. Coarse fractions are typically siliceous (>90% quartz+resistant minerals) but in some classes greater than 10% weatherable minerals are allowed.
 

II. Bisiallitic Assemblages
 

Soil material that consists of clay fractions containing appreciable amounts of vermiculite, mica and/or chlorite or identifiable amounts of smectite (usually > 10%). Various amounts of interstratified mica-vermiculite-chlorite, partially hydroxy-Al interlayered vermiculite or smectite, and interstratified mica-smectite have been identified in the Southern Region. Cation exchange capacities are generally greater than 30 meq/100g of clay. Typically, coarse fractions contain greater than 10% weatherable minerals, but soils that have siliceous mineralogy have been identified.
 

III. Organic Soil Material
 

Organic soil material is saturated with water for more than a few days and contains more than 20% (by weight) organic carbon; or is saturated with water for long periods (or is artificially drained) and, excluding live roots, has an organic carbon content of:

a. More than 18% if the mineral fraction contains 60% or more clay; or

b. More than 12% if the mineral fraction contains no clay; or

c. More than 12+ (clay percentage multiplied by 0.1) percent if the mineral fraction contains less than 60% clay.

Table 1, continued
 

I.1 Juventic - Monosiallitic soil material (<2mm fine earth fraction) with low content of Fe and Al oxyhydroxides, usually < 7% and have more than 10% weatherable minerals in the coarse fraction (>20um).
 
 

I.2 Sesquijuventic - Monosiallitic soil material (<2mm fine earth fraction) with moderate to high content of Fe and Al oxyhydroxides, usually > 7% and have more than 10% weatherable minerals in the coarse fraction (>20um).
 

I.3 Sesquimonorthic - Monosiallitic soil material (<2mm fine earth fraction) with moderate to high content of Fe and Al oxyhydroxides, usually > 7% and/or accumulations of more than 5% iron-rich and/or iron cemented bodies such as plinthite. Sesquimonorthic soil materials have less than 10% weatherable minerals in the coarse fraction (>20um).
 

I.4 Monorthic - Other monosiallitic soil material..
 

II.1 Calcaric - Strongly calcareous bisiallitic soil material with more than 2% free free carbonates throughout.
 

II.2 Smectic - Biasiallitic soil material in which smectite is the dominant mineral in the clay fraction. Typically smectite content is more than 50 percent of the clay fraction.
 

II.3 Parasmectic - Biasiallitic soil material in which the smectite is identified, but is not the dominant mineral, Smectite content ranges from 10 to 50 percent of the clay fraction. Quartz is not the dominant mineral in the clay.
 

II.4 Quartzismectic - Biasiallitic soil material in which quartz is the dominant mineral in the clay fraction. The smectite content is more than 10 percent of the clay fraction.
 

II. 4 Biorthic - Other bisiallitic soil material with less than 10% smectite.
 
 

III..1 Histosols - Soil material that meets the definition of histic material and occurs in soils that are classified as Histosols. (Soil Survey Staff, 1997. Keys To, Soil Taxonomy, eight edition, USDA-Soil Conservation Service, SMSS Technical Monograph no.19.