552 Petrology

Particle Aspect Ratio

"This file contains the CGI Particle Aspect Ratio vocabulary, as defined by the IUGS Commission for Geoscience Information (CGI) Geoscience Terminology Working Group. AspectRatio describes the geometry of particles based on the ratios of lengths of long, intermediate and short axes of grains. Equates to sphericity in sedimentary rocks (ie: the degree to which the shape of a particle approximates a sphere). A quantitative specification is based on the ratio of lengths of long, intermediate and short axes of grain shape (Sneed and Folk, 1958; Zingg, 1935).

Particle Shape

"This file contains the CGI Particle Shape vocabulary, as defined by the IUGS Commission for Geoscience Information (CGI) Geoscience Terminology Working Group. The Shape attribute describes, a) the development of crystal faces bounding particles in crystalline compond materials, and b) surface rounding of grains in sedimentary rocks. Roundness is a measure of the sharpness of the edges between surfaces bounding a particle (see Jackson, 1997; Wadell, 1932) and is an indication of the degree of abrasion of a clastic particle.

Particle Type

"This file contains the CGI Particle type vocabulary, as defined by the IUGS Commission for Geoscience Information (CGI) Geoscience Terminology Working Group. Used to specify particleType in particleTypeDescription associated with a compoundMaterial. Terms to specify the nature of individual particles of each constituent in an aggregation, based mostly on their genesis. Because the constituents are identifiable parts, the part units must have some definition. Examples include clasts, crystals, pore space, material fossil.

Proportion Term

"This file contains the CGI Proportion Term vocabulary, as defined by the IUGS Commission for Geoscience Information (CGI) Geoscience Terminology Working Group. This vocabulary provides terms that may be used to qualitatively express abundance of composition parts in a geologic unit or earth material description. Quantity that specifies the fraction of the geologic unit composed of the compound material. This vocabulary is used for GeologicUnit.GeologicUnitPart.proportion, GeologicUnit.compositionPart.proportion, and for compoundMaterial.ConsituentPart.proportion.

Simple Lithology

"This scheme specifies the concept space for Simple Lithology concepts, as defined by the IUGS Commission for Geoscience Information (CGI) Geoscience Terminology Working Group. By extension, it includes all concepts in this conceptScheme, as well as concepts in any previous versions of the scheme. This vocabulary is not designed to be a comprehensive list of all lithology terms."