Hakim,
here's a small introduction in grain shape and what the different parameters mean...
The shapes of minerals and clasts (rock fragments) in sedimentary rocks are determined
by a variety of factors: the original shapes of mineral grains in the source rocks; the orientation and spacing of fractures in bedrock that influence the shapes that clasts (rock fragments) take on when they weather from exposed rock; the nature and intensity of sediment transport, which can abrade grains and change original shapes; and sediment burial processes such as compaction, which can also change original shapes. Therefore, sedimentary particles may display a wide range of shapes, depending upon their history. Particle shape is defined by three related but different aspects of grains.
Form refers to the gross, overall configuration (outline) of particles and reflects variations in their proportions. The form of some particles resembles that of a sphere; other particles may have a platy (flattened) or rodlike form. Form should not be confused with roundness, which is a measure of the sharpness of grain corners. Well-rounded grains have smooth comers and edges; poorly rounded grains have sharp or angular corners and edges (Fig. 3.8B). Surface texture refers to small-scale, microrelief markings such as pits, scratches, and ridges that occur on the surface of grains. Form, roundness, and surface texture are independent properties and each can theoretically vary without affecting the other. Actually, form and roundness tend to be positively correlated in sedimentary deposits; particles that are highly spherical in shape also tend to be well rounded. Surface texture can change without significantly changing form or roundness, but a change in form or roundness will affect surface texture because new surfaces are exposed. The three aspects of shape can
be thought of as constituting a hierarchy, in which form is a first-order property, roundness a second-order property superimposed on form, and surface texture a third-order property superimposed on both the corners of a grain and the surfaces between corners.
hope this explained it a little bit... Shape, sound like the term Form as is used here.
