Particle Shape

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well rounded
definition A clastic sedimentary particle whose original faces, edges, and corners have been destroyed by abrasion and whose entire surface consists of broad curves without any flat areas, specif. said of a particle with no secondary corners and a roundness value between 0.70 and 1.00 (midpoint at 0.84). The original shape may be suggested by the present form of the particle. more like this
source Powers, M. C., 1953 A new roundness scale for sedimentary particles. Journal of Sedimentary Petrology, v. 23, p. 117-119 more like this
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angular
anhedral
diffuse
euhedral
resorbed
rounded
shape not specified
sub angular
sub rounded
subhedral
very angular
well rounded
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angular
definition A clastic sedimentary particle showing very little or no evidence of abrasion, with all of its edges and corners sharp, such as blocks with numerous (15-30) secondary corners and a roundness value between 0.17 and 0.25 (midpoint at 0.21). more like this
source Powers, M. C., 1953 A new roundness scale for sedimentary particles. Journal of Sedimentary Petrology, v. 23, p. 117-119 more like this
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anhedral
definition Crystalline particles in a rock lack well-developed crystal faces, usually referring to igneous or metamorphic grains more like this
source MacKenzie, W.S., Donaldson, C.H. & Guilford, C., 1982. Atlas of igneous rocks and their textures. John Wiley & Sons, New York more like this
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diffuse
definition Particles in aggregate have diffuse, ill-defined boundaries more like this
source SLTTs 2004 more like this
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euhedral
definition Crystalline particles in a rock are mostly bounded by perfect crystal faces, usually referring to igneous or metamorphoc grains more like this
source MacKenzie, W.S., Donaldson, C.H. & Guilford, C., 1982. Atlas of igneous rocks and their textures. John Wiley & Sons, New York more like this
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resorbed
definition Particles have smooth, embayed boundaries caused by resorption by the host magma more like this
source Neuendorf, K.K.E, Mehl, J.P. & Jackson, J.A. (eds), 2005. Glossary of geology, 5th Edition. American Geological Institute, Alexandria, 779 p. more like this
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rounded
definition A clastic sedimentary particle whose original edges and corners have been smoothed off to rather broad curves and whose original faces are almost completely removed by abrasion (although some comparatively flat surfaces may be present), such as a pebble with a roundness value between 0.49 and 0.70 (midpoint at 0.59) and few (0-5) and greatly subdued secondary corners. The original shape is still readily apparent. more like this
source Powers, M. C., 1953 A new roundness scale for sedimentary particles. Journal of Sedimentary Petrology, v. 23, p. 117-119 more like this
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any shape
definition Shape property may have any value. Use in normative definitions where shape may take any value. more like this
source this vocabulary more like this
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sub angular
definition A clastic sedimentary particle showing definite effects of slight abrasion, retaining its original general form, and having faces that are virtually untouched and edges and corners that are rounded off to some extent, such as a glacial boulder with numerous (10-20) secondary corners and a roundness value between 0.25 and 0.35 (midpoint at 0.300). more like this
source Powers, M. C., 1953 A new roundness scale for sedimentary particles. Journal of Sedimentary Petrology, v. 23, p. 117-119 more like this
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sub rounded
definition A clastic sedimentary particle showing considerable but incomplete abrasion and an original general form that is still discernible, and having many of its edges and corners noticeably rounded off to smooth curves, such as a cobble with a reduced number (5-10) of secondary corners, a considerably reduced area of the original faces, and a roundness value between 0.35 and 0.49 (midpoint at 0.41). more like this
source Powers, M. C., 1953 A new roundness scale for sedimentary particles. Journal of Sedimentary Petrology, v. 23, p. 117-119 more like this
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subhedral
definition Crystalline particles in a rock are partly bounded by crystal faces, usually referring to igneous or metamorphic grains more like this
source MacKenzie, W.S., Donaldson, C.H. & Guilford, C., 1982. Atlas of igneous rocks and their textures. John Wiley & Sons, New York more like this
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very angular
definition A clastic sedimentary particle with a roundness value between 0.12 and 0.17 (midpoint at 0.14). more like this
source Powers, M. C., 1953 A new roundness scale for sedimentary particles. Journal of Sedimentary Petrology, v. 23, p. 117-119 more like this
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in scheme particleshape
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