MUID 19      Biorthic-Parasmectic-Monorthic

Biorthic - Typical bisiallitic 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 hydroxyinterlayered 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.

Parasmectic - Biasiallitic soil material in which 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 fraction.

Monorthic -Kaolinite, halloysite and or fully hydroxy interlayered vermiculite (HIV) dominate the clay fraction. 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).