Textural Pedofeatures are pedofeatures consisting of accumulations of particles of any size and in variable proportions. Textural pedofeatures are important because they porvide a record of current and past eluviation-illuviation processes. The most important criteria with which to describe textural pedofeatures are texture and internal fabric (lamination and birefringence). The following descriptions are proposed:

Limpid clay: (Fine clay) UNiform clay without inclusions of micro-particles.
Dusty clay: (coarse and fine clay) Composed of clay containing micro-particles up to 3µm in diameter.
Impure clay: Clay containing numerous contrasted particles of fine silt-size. Mica flakes between crossed polarizers can be seen but quartz particles less so because of their lower birefringence.
Silt: Consisting of silt-sized particles. Further subdivision is possible into fine, medium and coarse silt-sized material. It should be noted whether the grains are coated with clay or whether bare.
Sand: Consisting of sand-size grains. Further subdivision is possible as for silt above.
Clay and Silt: Variable proportions of silt and clay size particles. Teh class can be subdivided into silty clay where some silt grains are disposed throughout a clayey mass and clayey silt in which the silt fraction is dominant but more clay is present than just as coats.
Unsorted: Variable proportions of sand, silt and clay.

Depletion Pedofeatures are pedofeatures arising from the loss of components, other than textural ones, compared with the adjacent matrix. Its identification depends mainly on the depleted area being clearly contrasting compared with the adjacent matrix. Loss of a component from a particular area may not, in itself, produce a recognizabledepletion pedofeature unless the component has a clear morphological expression such as shape, internal fabric, or color. The description of depletion pedofeatures should include size, external morphology, internal fabric, contrast, abundance, variability, distribution and orientation.

Crystalline Pedofeatures consist of crystals, considered to have formed in situ, of any size visible under the optical microscope. Isolated crystals are considered as crystalline pedofeatures only when larger than 0.02 mm. Smaller crystal are considered to be part of the groundmass or as cryptocrystalline pedofeatures. The description of crystalline pedofeatures (other than those composed of neoformed clay) should include mineralogical name, size, external morphology, internal fabric, frequency, contrast, variability and distribution. Crystalline pedofeatures are subdivided as follows:

Typic: Composed only of crystalline material without evidence of pseudomorphic or biological origin.
Pseudomorphic: Composed only of crystalline material pseudomorphosing, partially or completely, plant tissues, faunal remains or rock or soil fabrics.
Bio: Composed of crystalline material of biological origin; the form of the crystals and the fabric of the pedofeatures result from biological acitvity.
Impregnative: Composed of crystalline material mixed with or superimposed on soil material, rock or plant fragments. Two types are recognized according to the composition of teh host material - where this is identical to the adjacent material the feature is termed orthic, where different anorthic.

Crystalline pedofeatures are classed into groups and types (see table of classification of pedofeatures). Examples include:

Calcitic pedofeatures, both inherited and formed inplace. Calcitic pedofeatures may occur as coatings, hypo-coatings and quasi-coatings, infillings, crystals and crystal intergrowths, nodules and fragments.
Gypsic pedofeatures. Habits of gypsum in soil include lenticular, prismatic and fibrous. Gypsum may occur as infillings, crystals and crystal intergrowths and nodules.

Amorphous and Cryptocrystalline Pedofeatures are isotropic between crossed polarizers, except for inclusions of birefringent organic and/or mineral basic components. Crystals of the cubic system isotropic between crossed polarizers, are excluded from this group. The most common mineral amorphous or cryptocrystalline pedofeatures are segregations of iron and manganese oxides/hydroxides associated with poor drainage and anaerobic conditions. Three types of pedofeatures are recognized:

Pure: The pedofeatures are composed only of amorphous or cryptocrystalline material without evidence of pseudomorphic origin.
Pseudomorphic: The pedofeatures are composed only of amorphous or cryptocrystalline material that pseudomorphoses, partially or completely, vegetal tissues, faunal remains, rock or soil fabrics.
Impregnative: The pedofeatures are formed by amorphous or crytocrystalline material impregnating soil material, rock or plant remains.

Fabric Pedofeatures are differentiated from the adjacent material only by a difference in fabric. Most fabric pedofeatures result from mechancial or physical transformation associated with biological activity, shrink-swell, or human activity. A systematic description includes:

1. Composition
   
2. Size of constituents
   
3. External morphology: external shape and sharpness of boundaries
   
4. Internal fabric: the microstructure of the pedofeature as for soil microstructure
   
5. Contrast with the adjacent material
   
6. Frequency of occurrence of features or constitiuents
   
7. Variability (differences that exist between a constituent and all other constituents classed as belonging to the same type)
   
8. Distribution and orientation patterns

Excrement Pedofeatures are pedofeatures with a form associated with excrements of soil animals. Excrements of soil animals are important micromorphologicl features for tow reasons:

1. They reflect former or current animal activity and environmnental activity;
   
2. They often form an essential part of the soil structure.

This page (http://www.ces.ncsu.edu/plymouth/programs/six.html) created by
Vera MacConnell, Research Technician, I on February 5, 1998.
Last Updated on February 6, 1998.