Undifferentiated b-fabric is characterized by an absence of interference colors in the fine mass due to being composed of isotropic or opaque materials or to masking by humus, sesquioxides, etc. (Broadly equivalent to isotic favric of Brewer)

Crystallitic b-fabric is characterized by the presence of small birefringent crystals (e.g. calcite), microlites, or mineral fragments (small mica or sericite flakes) which cause the interference colors in the fine mass. A crystallitic b-fabric is commonly associated with soils composed of a matrix of clay and microcrystalline calcite. (Broadly equivalent to crystic plasmic fabric of Brewer)

Striated, speckled and strial fabrics are composed dominantly of clay, zones of orientation birefringence due to particle orientation are frequently observed between crossed polarizers. If these zones consist of small (a few µm), more or less equal domain, the term speckled b-fabric is used. Speckled b-fabric is characterized by the occurrence in the fine mass of randomly arranged equidimensional or slightly prolate speckles of optically oriented clya, smaller than the fabric units at the scale of observation. More elongated zones, sometimes several hundreds µm long, are described as striated, and constitue a striated b-fabric (Broadly equivalent to sepic fabrics of Brewer) which is characterized by the presence of elongated birefringent zones or streaks in which the particles show more or less simultaneous extinction. A general orientation of teh clay material usually inherited from sedimentation processes is referred to as a strial b- fabric for the fabric of plasmas exhibiting as a whole a preferred parallel orientation. A b-fabric formed by clay particles oriented parallel to the surface of a pore is termed a porostriated b-fabric. Anisotropic clay particles oriented parallel to the walls of resistant fabric units give rise to granostriated b-fabric.

This page (http://www.ces.ncsu.edu/plymouth/programs/birefringent.html) created by
Vera MacConnell, Research Technician, I on February 4, 1998.
Last Updated on February 4, 1998.