Particle shape: a review and new methods of characterization and classification

Abstract

Shape is a fundamental property of all objects, including sedimentary particles, but it remains one of the most difficult to characterize and quantify for all but the simplest of shapes. Despite a large literature on the subject, there remains widespread confusion regarding the meaning and relative value of different measures of particle shape. This paper re‐examines the basic concepts of particle shape and suggests a number of new and modified methods which are widely applicable to a range of sedimentological problems; it is shown that the most important aspects of particle form are represented by the I/L ratio (elongation ratio) and S/I ratio (flatness ratio). A combination of these two ratios can be used to classify particles in terms of 25 form classes. A method of obtaining a quantitative measure of particle roundness using simple image analysis software is described, and a new visual roundness comparator is presented. It is recommended that measurements of both roundness and circularity (a proxy measure of sphericity) are made on grain images in three orthogonal orientations and average values calculated for each particle. A further shape property, irregularity, is defined and a classification scheme proposed for use in describing and comparing irregular or branching sedimentary particles such as chert and coral.

Evolução da planície costeira das Praias do Sul e do Leste – Ilha Grande/RJ: implicações sobre a presença humana pre-histórica e contribuições para a reconstrução paleoambiental holocênica

“…Os resultados relativos ao tamanho de grãos foram processados no programa Gradistat 8.0 (Blott & Pye 2001), que baseia sua estatística em Folk & Ward (1957). A esfericidade e o arredondamento foram avaliados segundo os padrões publicados em Blott & Pye (2008).…”

Aplicación De Índices De Forma en La Determinación De Polígonos Slivers Derivados De Las Dimensiones Lineales De Una Figura Y Su Área

“…Sin embargo, sí es posible cuantificar alguno de los aspectos de la forma (elongación, compactación). Tal como demuestran Blott and Pye (2008) Son índices que utilizan conceptos sobradamente conocidos, como la anchura y la altura de las figuras. Según Frolov (1975), fue Vereschchagin (1930) quien propuso medir la elongación de una figura mediante el cociente del eje más largo por el eje más corto, ambos en direcciones perpendiculares, véase Ec.…”

Size-associated Variation and Factors Affecting the Morphology of Brown Bodies in Glycera tridactyla (Polychaeta:Glyceridae)

“…To quantify the brown body shape, the elongation degree (ED=I/L) was used based on the formula given by Blott and Pye (2008) for sedimentary particles where "I" was the minor and "L" was the major axes in this paper. The shape classification was also made according to Blott and Pye (2008) (Fig.…”